diff --git a/CHANGELOG.md b/CHANGELOG.md
index 432a134..66be871 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,29 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.1.2-beta] - 2025-08-15
+
+### Added
+- **MiAuth authentication support** - Alternative authentication method for Misskey servers
+- **Comprehensive error handling system** - Granular exception classes for different error scenarios
+
+### Changed
+- **Error handling architecture** - Replaced generic exceptions with specific `MisskeyAuthException` subclasses
+- **OAuth client improvements** - Enhanced error mapping and better exception handling
+- **MiAuth client implementation** - Complete MiAuth authentication flow with proper error handling
+
+### Features
+- `MisskeyMiAuthClient` - Main MiAuth authentication client
+- `MisskeyMiAuthConfig` - Configuration class for MiAuth authentication
+- `MiAuthTokenResponse` - Response model for MiAuth authentication
+- Enhanced exception classes including:
+  - `OAuthNotSupportedException` - Server doesn't support OAuth 2.0
+  - `MiAuthDeniedException` - User denied MiAuth permission
+  - `NetworkException` - Network connectivity issues
+  - `UserCancelledException` - User cancelled authentication
+  - `CallbackSchemeErrorException` - URL scheme configuration errors
+  - And 15+ more specific exception classes
+
 ## [0.1.1-beta] - 2025-08-12
 
 ### Changed
diff --git a/README.md b/README.md
index a91ac16..f4943cf 100644
--- a/README.md
+++ b/README.md
@@ -30,7 +30,7 @@ Add this to your package's `pubspec.yaml` file:
 
 ```yaml
 dependencies:
-  misskey_auth: ^0.1.1-beta
+  misskey_auth: ^0.1.2-beta
 ```
 
 ### Quick Start
@@ -134,6 +134,63 @@ Add to `android/app/src/main/AndroidManifest.xml`:
 </activity>
 ```
 
+#### Differences in MiAuth and OAuth Configuration (Key Points for App Integration)
+- This configuration (registration of the URL scheme) is done on the "app side." It is not included in the library's Manifest.
+- Both methods require a "custom URL scheme" to return from an external browser to the app.
+- The difference lies in how to specify "where to return from the browser."
+- OAuth: Since it needs to return to an HTTPS `redirect_uri` from the authorization server, `redirect.html` placed there ultimately redirects back to `yourscheme://...` for the app.
+- MiAuth: The `callback` query of the authentication start URL specifies `yourscheme://...` from the beginning (no need for `https`).
+
+##### Example of MiAuth
+
+```dart
+import 'package:misskey_auth/misskey_auth.dart';
+
+final miClient = MisskeyMiAuthClient();
+final miConfig = MisskeyMiAuthConfig(
+  host: 'misskey.io',
+  appName: 'Your App',
+  callbackScheme: 'yourscheme',          // Scheme registered on the app side
+  permissions: ['read:account', 'write:notes'],
+  iconUrl: 'https://example.com/icon.png', // Optional
+);
+final miRes = await miClient.authenticate(miConfig);
+```
+
+##### Example of OAuth
+
+```dart
+import 'package:misskey_auth/misskey_auth.dart';
+
+final oauthClient = MisskeyOAuthClient();
+final oauthConfig = MisskeyOAuthConfig(
+  host: 'misskey.io',
+  clientId: 'https://yourpage/yourapp/',
+  redirectUri: 'https://yourpage/yourapp/redirect.html',
+  scope: 'read:account write:notes',
+  callbackScheme: 'yourscheme',          // Scheme registered on the app side
+);
+final token = await oauthClient.authenticate(oauthConfig);
+```
+
+##### How to Support Both Methods in the Same App
+- By registering the same `scheme` (e.g., `yourscheme`) in iOS's `Info.plist` and Android's `AndroidManifest.xml`, it can be shared between OAuth and MiAuth.
+- If you implement the OAuth `redirect.html` to redirect to `yourscheme://oauth/callback?...`, you can reuse the same path expression (`yourscheme://oauth/callback`) for MiAuth's `callback`.
+- For Android, matching only on the `scheme` is sufficient as shown below (the `host` and `path` are optional).
+
+```xml
+<activity android:name="com.linusu.flutter_web_auth.CallbackActivity" android:exported="true">
+    <intent-filter android:label="flutter_web_auth">
+        <action android:name="android.intent.action.VIEW" />
+        <category android:name="android.intent.category.DEFAULT" />
+        <category android:name="android.intent.category.BROWSABLE" />
+        <data android:scheme="yourscheme" />
+    </intent-filter>
+    <!-- Add this only if you want to restrict by host/path -->
+    <!-- <intent-filter> ... <data android:scheme="yourscheme" android:host="oauth" android:path="/callback"/> ... </intent-filter> -->
+  </activity>
+```
+
 ### API Reference
 
 #### MisskeyOAuthConfig
@@ -152,26 +209,52 @@ class MisskeyOAuthConfig {
 
 #### MisskeyOAuthClient
 
-Main client for handling Misskey authentication.
+Main client for handling Misskey OAuth authentication.
 
 ```dart
 class MisskeyOAuthClient {
   /// Authenticate with Misskey server
-  Future<OAuthTokenResponse> authenticate(MisskeyOAuthConfig config);
+  Future<OAuthTokenResponse?> authenticate(MisskeyOAuthConfig config);
+  
+  /// Get OAuth server information
+  Future<OAuthServerInfo?> getOAuthServerInfo(String host);
   
-  /// Check if server supports OAuth 2.0
-  Future<bool> isOAuthSupported(String host);
+  /// Get stored access token
+  Future<String?> getStoredAccessToken();
+  
+  /// Clear stored tokens
+  Future<void> clearTokens();
+}
+```
+
+#### MisskeyMiAuthClient
+
+Main client for handling Misskey MiAuth authentication.
+
+```dart
+class MisskeyMiAuthClient {
+  /// Authenticate with Misskey server using MiAuth
+  Future<MiAuthTokenResponse> authenticate(MisskeyMiAuthConfig config);
+  
+  /// Get stored access token
+  Future<String?> getStoredAccessToken();
+  
+  /// Clear stored tokens
+  Future<void> clearTokens();
 }
 ```
 
 ### Error Handling
 
-The library provides custom exceptions for different error scenarios:
+The library provides comprehensive error handling with custom exception classes for different scenarios. For detailed information about each exception class and their usage, please refer to the documentation on pub.dev.
 
-- `MisskeyAuthException` - Base exception class
-- `OAuthNotSupportedException` - When server doesn't support OAuth 2.0
-- `AuthenticationFailedException` - When authentication fails
-- `TokenExchangeException` - When token exchange fails
+The library includes exception classes for:
+- Authentication configuration errors
+- Network and connectivity issues
+- OAuth and MiAuth specific errors
+- User cancellation and authorization failures
+- Secure storage operations
+- Response parsing errors
 
 ### Common Errors
 
@@ -251,7 +334,7 @@ MisskeyのOAuth認証・MiAuth認証をFlutterアプリで簡単に扱うため
 
 ```yaml
 dependencies:
-  misskey_auth: ^0.1.1-beta
+  misskey_auth: ^0.1.2-beta
 ```
 
 ### クイックスタート
@@ -355,6 +438,65 @@ final token = await client.authenticate(config);
 </activity>
 ```
 
+#### MiAuth と OAuth の設定の違い（アプリ組み込み時のポイント）
+
+- この設定（URLスキームの登録）は「アプリ側」で行います。ライブラリ内のManifestには含めません。
+- 両方式とも、外部ブラウザからアプリへ戻すために「カスタムURLスキーム」が必要です。
+- 相違点は「ブラウザからどこに戻すか」の指定方法です。
+  - OAuth: 認可サーバーからはHTTPSの`redirect_uri`に戻る必要があるため、そこに配置した`redirect.html`が最終的に`yourscheme://...`へリダイレクトしてアプリに戻します。
+  - MiAuth: 認証開始URLの`callback`クエリに、最初から`yourscheme://...`を指定します（`https`は不要）。
+
+##### MiAuth の例（Dart）
+
+```dart
+import 'package:misskey_auth/misskey_auth.dart';
+
+final miClient = MisskeyMiAuthClient();
+final miConfig = MisskeyMiAuthConfig(
+  host: 'misskey.io',
+  appName: 'Your App',
+  callbackScheme: 'yourscheme',          // アプリ側で登録したスキーム
+  permissions: ['read:account', 'write:notes'],
+  iconUrl: 'https://example.com/icon.png', // 任意
+);
+final miRes = await miClient.authenticate(miConfig);
+```
+
+##### OAuth の例
+
+```dart
+import 'package:misskey_auth/misskey_auth.dart';
+
+final oauthClient = MisskeyOAuthClient();
+final oauthConfig = MisskeyOAuthConfig(
+  host: 'misskey.io',
+  clientId: 'https://yourpage/yourapp/',
+  redirectUri: 'https://yourpage/yourapp/redirect.html',
+  scope: 'read:account write:notes',
+  callbackScheme: 'yourscheme',          // アプリ側で登録したスキーム
+);
+final token = await oauthClient.authenticate(oauthConfig);
+```
+
+##### 両方式を同一アプリでサポートするには
+
+- iOSの`Info.plist`・Androidの`AndroidManifest.xml`で同じ`sheme`（例: `yourscheme`）を1つ登録すれば、OAuth/MiAuthで共用可能です。
+- OAuth用の`redirect.html`は、`yourscheme://oauth/callback?...`へ飛ばす実装にしておくと、MiAuthの`callback`でも同じパス表現（`yourscheme://oauth/callback`）を使い回せます。
+- Androidは以下のように`scheme`のみのマッチで十分です（`host`や`path`は任意）。
+
+```xml
+<activity android:name="com.linusu.flutter_web_auth.CallbackActivity" android:exported="true">
+    <intent-filter android:label="flutter_web_auth">
+        <action android:name="android.intent.action.VIEW" />
+        <category android:name="android.intent.category.DEFAULT" />
+        <category android:name="android.intent.category.BROWSABLE" />
+        <data android:scheme="yourscheme" />
+    </intent-filter>
+    <!-- 必要に応じて、host/pathで限定したい場合のみ追記 -->
+    <!-- <intent-filter> ... <data android:scheme="yourscheme" android:host="oauth" android:path="/callback"/> ... </intent-filter> -->
+  </activity>
+```
+
 ### API リファレンス
 
 #### MisskeyOAuthConfig
@@ -373,26 +515,52 @@ class MisskeyOAuthConfig {
 
 #### MisskeyOAuthClient
 
-Misskey認証を処理するメインクライアント。
+Misskey OAuth認証を処理するメインクラス
 
 ```dart
 class MisskeyOAuthClient {
   /// Misskeyサーバーで認証を実行
-  Future<OAuthTokenResponse> authenticate(MisskeyOAuthConfig config);
+  Future<OAuthTokenResponse?> authenticate(MisskeyOAuthConfig config);
+  
+  /// OAuthサーバー情報を取得
+  Future<OAuthServerInfo?> getOAuthServerInfo(String host);
+  
+  /// 保存されたアクセストークンを取得
+  Future<String?> getStoredAccessToken();
+  
+  /// 保存されたトークンを削除
+  Future<void> clearTokens();
+}
+```
+
+#### MisskeyMiAuthClient
+
+Misskey MiAuth認証を処理するメインクラス
+
+```dart
+class MisskeyMiAuthClient {
+  /// MisskeyサーバーでMiAuth認証を実行
+  Future<MiAuthTokenResponse> authenticate(MisskeyMiAuthConfig config);
+  
+  /// 保存されたアクセストークンを取得
+  Future<String?> getStoredAccessToken();
   
-  /// サーバーがOAuth 2.0をサポートしているかチェック
-  Future<bool> isOAuthSupported(String host);
+  /// 保存されたトークンを削除
+  Future<void> clearTokens();
 }
 ```
 
 ### エラーハンドリング
 
-ライブラリは様々なエラーシナリオに対応するカスタム例外を提供します：
+ライブラリには以下のカテゴリの例外クラスが含まれています：
+- 認証設定エラー
+- ネットワーク・接続エラー
+- OAuth・MiAuth固有のエラー
+- ユーザーキャンセル・認可失敗
+- セキュアストレージ操作エラー
+- レスポンス解析エラー
 
-- `MisskeyAuthException` - ベース例外クラス
-- `OAuthNotSupportedException` - サーバーがOAuth 2.0をサポートしていない場合
-- `AuthenticationFailedException` - 認証が失敗した場合
-- `TokenExchangeException` - トークン交換が失敗した場合
+詳細についてはpub.devのドキュメントを参考にして下さい
 
 ### よくあるエラー
 
diff --git a/android/app/src/main/AndroidManifest.xml b/android/app/src/main/AndroidManifest.xml
index 5a66e8a..898912f 100644
--- a/android/app/src/main/AndroidManifest.xml
+++ b/android/app/src/main/AndroidManifest.xml
@@ -24,14 +24,6 @@
                 <action android:name="android.intent.action.MAIN"/>
                 <category android:name="android.intent.category.LAUNCHER"/>
             </intent-filter>
-
-            <!-- OAuth redirect handling -->
-            <intent-filter android:label="flutter_web_auth_2">
-                <action android:name="android.intent.action.VIEW" />
-                <category android:name="android.intent.category.DEFAULT" />
-                <category android:name="android.intent.category.BROWSABLE" />
-                <data android:scheme="misskeyauth" android:host="oauth" android:path="/callback" />
-            </intent-filter>
         </activity>
         <!-- Don't delete the meta-data below.
              This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
diff --git a/example/android/app/src/main/AndroidManifest.xml b/example/android/app/src/main/AndroidManifest.xml
index 5be01ff..3670012 100644
--- a/example/android/app/src/main/AndroidManifest.xml
+++ b/example/android/app/src/main/AndroidManifest.xml
@@ -25,6 +25,17 @@
                 <category android:name="android.intent.category.LAUNCHER"/>
             </intent-filter>
         </activity>
+
+        <!-- flutter_web_auth_2 用のコールバック受け取り Activity -->
+        <activity android:name="com.linusu.flutter_web_auth.CallbackActivity" android:exported="true">
+            <intent-filter android:label="flutter_web_auth_2">
+                <action android:name="android.intent.action.VIEW" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <category android:name="android.intent.category.BROWSABLE" />
+                <!-- 例のコールバックスキーム。必要に応じて変更 -->
+                <data android:scheme="misskeyauth" />
+            </intent-filter>
+        </activity>
         <!-- Don't delete the meta-data below.
              This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
         <meta-data
diff --git a/example/lib/main.dart b/example/lib/main.dart
index 3f49d2f..c2a1e7c 100644
--- a/example/lib/main.dart
+++ b/example/lib/main.dart
@@ -1,5 +1,6 @@
 import 'package:flutter/material.dart';
 import 'package:misskey_auth/misskey_auth.dart';
+import 'package:loader_overlay/loader_overlay.dart';
 
 void main() {
   runApp(const MyApp());
@@ -16,7 +17,9 @@ class MyApp extends StatelessWidget {
         colorScheme: ColorScheme.fromSeed(seedColor: Colors.blue),
         useMaterial3: true,
       ),
-      home: const AuthExamplePage(),
+      home: LoaderOverlay(
+        child: const AuthExamplePage(),
+      ),
     );
   }
 }
@@ -30,6 +33,8 @@ class AuthExamplePage extends StatefulWidget {
 
 class _AuthExamplePageState extends State<AuthExamplePage> {
   final _client = MisskeyOAuthClient();
+  final _miClient = MisskeyMiAuthClient();
+  int _currentIndex = 0;
 
   // フォームコントローラー
   final _hostController = TextEditingController();
@@ -38,12 +43,75 @@ class _AuthExamplePageState extends State<AuthExamplePage> {
   final _scopeController = TextEditingController();
   final _callbackSchemeController = TextEditingController();
 
+  // MiAuth 用フォーム
+  final _miAppNameController = TextEditingController();
+  final _miPermissionsController = TextEditingController();
+  final _miIconUrlController = TextEditingController();
+
   // 状態
-  bool _isLoading = false;
   String? _accessToken;
-  String? _errorMessage;
   OAuthServerInfo? _serverInfo;
 
+  String _mapErrorToMessage(Object error) {
+    // MisskeyAuth のカスタム例外をユーザー向け日本語に整形
+    if (error is MisskeyAuthException) {
+      final details = error.details;
+      if (error is UserCancelledException) {
+        return '認証がキャンセルされました';
+      }
+      if (error is CallbackSchemeErrorException) {
+        return 'コールバックスキームの設定が正しくありません（AndroidManifest/Info.plist を確認してください）';
+      }
+      if (error is AuthorizationLaunchException) {
+        return '認証画面を起動できませんでした';
+      }
+      if (error is NetworkException) {
+        return 'ネットワークエラーが発生しました';
+      }
+      if (error is ResponseParseException) {
+        return 'サーバー応答の解析に失敗しました';
+      }
+      if (error is SecureStorageException) {
+        return 'セキュアストレージの操作に失敗しました';
+      }
+      if (error is InvalidAuthConfigException) {
+        return '認証設定が無効です';
+      }
+      if (error is ServerInfoException) {
+        return 'サーバー情報の取得に失敗しました${details != null ? ': $details' : ''}';
+      }
+      // OAuth
+      if (error is OAuthNotSupportedException) {
+        return 'このサーバーはOAuth認証に対応していません（MiAuthをご利用ください）';
+      }
+      if (error is StateMismatchException) {
+        return 'セキュリティ検証に失敗しました（state不一致）';
+      }
+      if (error is AuthorizationCodeMissingException) {
+        return '認証コードを取得できませんでした';
+      }
+      if (error is AuthorizationServerErrorException) {
+        return '認可サーバーでエラーが発生しました${details != null ? ': $details' : ''}';
+      }
+      if (error is TokenExchangeException) {
+        return 'トークン交換に失敗しました${details != null ? ': $details' : ''}';
+      }
+      // MiAuth
+      if (error is MiAuthDeniedException) {
+        return 'MiAuth がキャンセル/拒否されました';
+      }
+      if (error is MiAuthCheckFailedException) {
+        return 'MiAuth の検証に失敗しました${details != null ? ': $details' : ''}';
+      }
+      if (error is MiAuthSessionInvalidException) {
+        return 'MiAuth のセッションが無効または期限切れです${details != null ? ': $details' : ''}';
+      }
+      return error.toString();
+    }
+    // その他の例外はそのまま文字列化
+    return error.toString();
+  }
+
   @override
   void initState() {
     super.initState();
@@ -58,6 +126,9 @@ class _AuthExamplePageState extends State<AuthExamplePage> {
     _redirectUriController.dispose();
     _scopeController.dispose();
     _callbackSchemeController.dispose();
+    _miAppNameController.dispose();
+    _miPermissionsController.dispose();
+    _miIconUrlController.dispose();
     super.dispose();
   }
 
@@ -69,22 +140,36 @@ class _AuthExamplePageState extends State<AuthExamplePage> {
         'https://librarylibrarian.github.io/misskey_auth/redirect.html';
     _scopeController.text = 'read:account write:notes';
     _callbackSchemeController.text = 'misskeyauth';
+
+    // MiAuth
+    _miAppNameController.text = 'Misskey Auth Example';
+    _miPermissionsController.text = 'read:account write:notes';
+    _miIconUrlController.text = '';
   }
 
   Future<void> _loadStoredToken() async {
-    final token = await _client.getStoredAccessToken();
-    setState(() {
-      _accessToken = token;
-    });
+    try {
+      final token = await _client.getStoredAccessToken();
+      setState(() {
+        _accessToken = token;
+      });
+    } on MisskeyAuthException catch (e) {
+      if (mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          SnackBar(content: Text(_mapErrorToMessage(e))),
+        );
+      }
+    } catch (_) {}
   }
 
   Future<void> _checkServerInfo() async {
     setState(() {
-      _isLoading = true;
       _serverInfo = null;
-      _errorMessage = null;
     });
 
+    if (!mounted) return;
+    context.loaderOverlay.show();
+
     try {
       final host = _hostController.text.trim();
       if (host.isEmpty) {
@@ -93,28 +178,39 @@ class _AuthExamplePageState extends State<AuthExamplePage> {
 
       final serverInfo = await _client.getOAuthServerInfo(host);
 
+      if (!mounted) return;
       setState(() {
         _serverInfo = serverInfo;
-        if (serverInfo == null) {
-          _errorMessage = 'OAuth認証はサポートされていません（MiAuth認証を使用してください）';
-        }
       });
+
+      if (serverInfo == null && mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          const SnackBar(
+              content: Text('OAuth認証はサポートされていません（MiAuth認証を使用してください）')),
+        );
+      }
+    } on MisskeyAuthException catch (e) {
+      if (mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          SnackBar(content: Text(_mapErrorToMessage(e))),
+        );
+      }
     } catch (e) {
-      setState(() {
-        _errorMessage = 'エラー: $e';
-      });
+      if (mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          SnackBar(content: Text(e.toString())),
+        );
+      }
     } finally {
-      setState(() {
-        _isLoading = false;
-      });
+      if (mounted) {
+        context.loaderOverlay.hide();
+      }
     }
   }
 
   Future<void> _startAuth() async {
-    setState(() {
-      _isLoading = true;
-      _errorMessage = null;
-    });
+    if (!mounted) return;
+    context.loaderOverlay.show();
 
     try {
       final config = MisskeyOAuthConfig(
@@ -127,7 +223,7 @@ class _AuthExamplePageState extends State<AuthExamplePage> {
 
       final tokenResponse = await _client.authenticate(config);
 
-      if (tokenResponse != null) {
+      if (tokenResponse != null && mounted) {
         setState(() {
           _accessToken = tokenResponse.accessToken;
         });
@@ -138,31 +234,110 @@ class _AuthExamplePageState extends State<AuthExamplePage> {
           );
         }
       }
+    } on MisskeyAuthException catch (e) {
+      if (mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          SnackBar(content: Text(_mapErrorToMessage(e))),
+        );
+      }
     } catch (e) {
-      setState(() {
-        _errorMessage = e.toString();
-      });
-
       if (mounted) {
         ScaffoldMessenger.of(context).showSnackBar(
           SnackBar(content: Text('認証エラー: $e')),
         );
       }
     } finally {
-      setState(() {
-        _isLoading = false;
-      });
+      if (mounted) {
+        context.loaderOverlay.hide();
+      }
     }
   }
 
-  Future<void> _clearToken() async {
-    await _client.clearTokens();
-    await _loadStoredToken();
+  Future<void> _startMiAuth() async {
+    if (!mounted) return;
+    context.loaderOverlay.show();
+
+    try {
+      final host = _hostController.text.trim();
+      if (host.isEmpty) {
+        throw Exception('ホストを入力してください');
+      }
+
+      final scheme = _callbackSchemeController.text.trim();
+      if (scheme.isEmpty) {
+        throw Exception('コールバックスキームを入力してください');
+      }
+
+      final permissions = _miPermissionsController.text
+          .split(RegExp(r"[ ,]+"))
+          .where((e) => e.isNotEmpty)
+          .toList();
 
-    if (mounted) {
-      ScaffoldMessenger.of(context).showSnackBar(
-        const SnackBar(content: Text('トークンを削除しました')),
+      final config = MisskeyMiAuthConfig(
+        host: host,
+        appName: _miAppNameController.text.trim(),
+        callbackScheme: scheme,
+        permissions: permissions,
+        iconUrl: _miIconUrlController.text.trim().isEmpty
+            ? null
+            : _miIconUrlController.text.trim(),
       );
+
+      final res = await _miClient.authenticate(config);
+
+      if (mounted) {
+        setState(() {
+          _accessToken = res.token;
+        });
+
+        if (mounted) {
+          ScaffoldMessenger.of(context).showSnackBar(
+            const SnackBar(content: Text('MiAuth に成功しました！')),
+          );
+        }
+      }
+    } on MisskeyAuthException catch (e) {
+      if (mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          SnackBar(content: Text(_mapErrorToMessage(e))),
+        );
+      }
+    } catch (e) {
+      if (mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          SnackBar(content: Text('MiAuth エラー: $e')),
+        );
+      }
+    } finally {
+      if (mounted) {
+        context.loaderOverlay.hide();
+      }
+    }
+  }
+
+  Future<void> _clearToken() async {
+    if (!mounted) return;
+    context.loaderOverlay.show();
+
+    try {
+      await _client.clearTokens();
+      await _loadStoredToken();
+
+      if (mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          const SnackBar(content: Text('トークンを削除しました')),
+        );
+      }
+    } on MisskeyAuthException catch (e) {
+      if (mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          SnackBar(content: Text(_mapErrorToMessage(e))),
+        );
+      }
+    } finally {
+      if (mounted) {
+        context.loaderOverlay.hide();
+      }
     }
   }
 
@@ -178,185 +353,271 @@ class _AuthExamplePageState extends State<AuthExamplePage> {
         child: Column(
           crossAxisAlignment: CrossAxisAlignment.stretch,
           children: [
-            // 保存されたトークン情報
-            Card(
-              child: Padding(
-                padding: const EdgeInsets.all(16.0),
-                child: Column(
-                  crossAxisAlignment: CrossAxisAlignment.start,
-                  children: [
-                    const Text(
-                      '保存されたトークン',
-                      style:
-                          TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
-                    ),
-                    const SizedBox(height: 8),
-                    Text(_accessToken != null
-                        ? '${_accessToken!.substring(0, 10)}...'
-                        : 'トークンなし'),
-                    if (_accessToken != null) ...[
-                      const SizedBox(height: 8),
-                      ElevatedButton(
-                        onPressed: _clearToken,
-                        style: ElevatedButton.styleFrom(
-                          backgroundColor: Colors.red,
-                          foregroundColor: Colors.white,
-                        ),
-                        child: const Text('トークンを削除'),
-                      ),
-                    ],
-                  ],
+            _buildStoredTokenCard(),
+            const SizedBox(height: 16),
+            if (_currentIndex == 0)
+              _buildOAuthForm(context)
+            else if (_currentIndex == 1)
+              _buildMiAuthForm(context)
+            else
+              _buildServerInfoTab(context),
+            // 画面内のエラーカード表示は行わず、Snackbarのみで通知
+          ],
+        ),
+      ),
+      bottomNavigationBar: NavigationBar(
+        selectedIndex: _currentIndex,
+        destinations: const [
+          NavigationDestination(icon: Icon(Icons.lock), label: 'OAuth'),
+          NavigationDestination(icon: Icon(Icons.vpn_key), label: 'MiAuth'),
+          NavigationDestination(
+              icon: Icon(Icons.info_outline), label: 'サーバー情報'),
+        ],
+        onDestinationSelected: (index) {
+          setState(() {
+            _currentIndex = index;
+          });
+        },
+      ),
+    );
+  }
+
+  Widget _buildStoredTokenCard() {
+    return Card(
+      child: Padding(
+        padding: const EdgeInsets.all(16.0),
+        child: Column(
+          crossAxisAlignment: CrossAxisAlignment.start,
+          children: [
+            const Text(
+              '保存されたトークン',
+              style: TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
+            ),
+            const SizedBox(height: 8),
+            Text(_accessToken != null
+                ? '${_accessToken!.substring(0, 10)}...'
+                : 'トークンなし'),
+            if (_accessToken != null) ...[
+              const SizedBox(height: 8),
+              ElevatedButton(
+                onPressed: _clearToken,
+                style: ElevatedButton.styleFrom(
+                  backgroundColor: Colors.red,
+                  foregroundColor: Colors.white,
                 ),
+                child: const Text('トークンを削除'),
               ),
-            ),
+            ],
+          ],
+        ),
+      ),
+    );
+  }
 
+  Widget _buildOAuthForm(BuildContext context) {
+    return Card(
+      child: Padding(
+        padding: const EdgeInsets.all(16.0),
+        child: Column(
+          crossAxisAlignment: CrossAxisAlignment.start,
+          children: [
+            const Text(
+              'OAuth認証設定',
+              style: TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
+            ),
+            const SizedBox(height: 8),
+            TextField(
+              controller: _callbackSchemeController,
+              decoration: const InputDecoration(
+                labelText: 'コールバックスキーム',
+                hintText: '例: misskeyauth',
+              ),
+            ),
             const SizedBox(height: 16),
-
-            // 認証設定フォーム
-            Card(
-              child: Padding(
-                padding: const EdgeInsets.all(16.0),
-                child: Column(
-                  crossAxisAlignment: CrossAxisAlignment.start,
-                  children: [
-                    const Text(
-                      'OAuth認証設定',
-                      style:
-                          TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
-                    ),
-                    const SizedBox(height: 8),
-                    TextField(
-                      controller: _callbackSchemeController,
-                      decoration: const InputDecoration(
-                        labelText: 'コールバックスキーム',
-                        hintText: '例: misskeyauth',
-                      ),
-                    ),
-                    const SizedBox(height: 16),
-                    TextField(
-                      controller: _hostController,
-                      decoration: const InputDecoration(
-                        labelText: 'ホスト',
-                        hintText: '例: misskey.io',
-                      ),
-                    ),
-                    const SizedBox(height: 8),
-                    TextField(
-                      controller: _clientIdController,
-                      decoration: const InputDecoration(
-                        labelText: 'クライアントID (URL)',
-                        hintText: '例: https://example.com/my-app',
-                      ),
-                    ),
-                    const SizedBox(height: 8),
-                    TextField(
-                      controller: _redirectUriController,
-                      decoration: const InputDecoration(
-                        labelText: 'リダイレクトURI',
-                        hintText: '例: https://example.com/redirect',
-                        helperText: '要HTTPS',
-                      ),
-                    ),
-                    const SizedBox(height: 8),
-                    TextField(
-                      controller: _scopeController,
-                      decoration: const InputDecoration(
-                        labelText: 'スコープ',
-                        hintText: '例: read:account write:notes',
-                      ),
-                    ),
-                    const SizedBox(height: 16),
-                    Row(
-                      children: [
-                        ElevatedButton(
-                          onPressed: _isLoading ? null : _checkServerInfo,
-                          child: const Text('サーバー情報を確認'),
-                        ),
-                        const SizedBox(width: 8),
-                        ElevatedButton(
-                          onPressed: _isLoading ? null : _startAuth,
-                          style: ElevatedButton.styleFrom(
-                            backgroundColor:
-                                Theme.of(context).colorScheme.primary,
-                            foregroundColor: Colors.white,
-                          ),
-                          child: const Text('認証を開始'),
-                        ),
-                      ],
-                    ),
-                  ],
-                ),
+            TextField(
+              controller: _hostController,
+              decoration: const InputDecoration(
+                labelText: 'ホスト',
+                hintText: '例: misskey.io',
               ),
             ),
-
-            // サーバー情報
-            if (_serverInfo != null) ...[
-              const SizedBox(height: 16),
-              Card(
-                child: Padding(
-                  padding: const EdgeInsets.all(16.0),
-                  child: Column(
-                    crossAxisAlignment: CrossAxisAlignment.start,
-                    children: [
-                      const Text(
-                        'サーバー情報',
-                        style: TextStyle(
-                            fontSize: 18, fontWeight: FontWeight.bold),
-                      ),
-                      const SizedBox(height: 8),
-                      Text('認証エンドポイント:\n${_serverInfo!.authorizationEndpoint}'),
-                      const SizedBox(height: 4),
-                      Text('トークンエンドポイント:\n${_serverInfo!.tokenEndpoint}'),
-                      if (_serverInfo!.scopesSupported != null) ...[
-                        const SizedBox(height: 4),
-                        Text(
-                            'サポートされているスコープ:\n${_serverInfo!.scopesSupported!.join(', ')}'),
-                      ],
-                    ],
+            const SizedBox(height: 8),
+            TextField(
+              controller: _clientIdController,
+              decoration: const InputDecoration(
+                labelText: 'クライアントID (URL)',
+                hintText: '例: https://example.com/my-app',
+              ),
+            ),
+            const SizedBox(height: 8),
+            TextField(
+              controller: _redirectUriController,
+              decoration: const InputDecoration(
+                labelText: 'リダイレクトURI',
+                hintText: '例: https://example.com/redirect',
+                helperText: '要HTTPS',
+              ),
+            ),
+            const SizedBox(height: 8),
+            TextField(
+              controller: _scopeController,
+              decoration: const InputDecoration(
+                labelText: 'スコープ',
+                hintText: '例: read:account write:notes',
+              ),
+            ),
+            const SizedBox(height: 16),
+            Row(
+              children: [
+                ElevatedButton(
+                  onPressed: _startAuth,
+                  style: ElevatedButton.styleFrom(
+                    backgroundColor: Theme.of(context).colorScheme.primary,
+                    foregroundColor: Colors.white,
                   ),
+                  child: const Text('認証を開始'),
                 ),
-              ),
-            ],
+              ],
+            ),
+          ],
+        ),
+      ),
+    );
+  }
 
-            // エラーメッセージ
-            if (_errorMessage != null) ...[
-              const SizedBox(height: 16),
-              Card(
-                color: Colors.red[50],
-                child: Padding(
-                  padding: const EdgeInsets.all(16.0),
-                  child: Column(
-                    crossAxisAlignment: CrossAxisAlignment.start,
-                    children: [
-                      const Text(
-                        'エラー',
-                        style: TextStyle(
-                          fontSize: 18,
-                          fontWeight: FontWeight.bold,
-                          color: Colors.red,
-                        ),
-                      ),
-                      const SizedBox(height: 8),
-                      Text(
-                        _errorMessage!,
-                        style: const TextStyle(color: Colors.red),
-                      ),
-                    ],
+  Widget _buildMiAuthForm(BuildContext context) {
+    return Card(
+      child: Padding(
+        padding: const EdgeInsets.all(16.0),
+        child: Column(
+          crossAxisAlignment: CrossAxisAlignment.start,
+          children: [
+            const Text(
+              'MiAuth認証設定',
+              style: TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
+            ),
+            const SizedBox(height: 8),
+            TextField(
+              controller: _callbackSchemeController,
+              decoration: const InputDecoration(
+                labelText: 'コールバックスキーム',
+                hintText: '例: misskeyauth',
+              ),
+            ),
+            const SizedBox(height: 8),
+            TextField(
+              controller: _hostController,
+              decoration: const InputDecoration(
+                labelText: 'ホスト',
+                hintText: '例: misskey.io',
+              ),
+            ),
+            const SizedBox(height: 8),
+            TextField(
+              controller: _miAppNameController,
+              decoration: const InputDecoration(
+                labelText: 'アプリ名',
+                hintText: '例: Misskey Auth Example',
+              ),
+            ),
+            const SizedBox(height: 8),
+            TextField(
+              controller: _miPermissionsController,
+              decoration: const InputDecoration(
+                labelText: '権限（空白/カンマ区切り）',
+                hintText: '例: read:account write:notes',
+              ),
+            ),
+            const SizedBox(height: 8),
+            TextField(
+              controller: _miIconUrlController,
+              decoration: const InputDecoration(
+                labelText: 'アイコンURL（任意）',
+              ),
+            ),
+            const SizedBox(height: 16),
+            Row(
+              children: [
+                ElevatedButton(
+                  onPressed: _startMiAuth,
+                  style: ElevatedButton.styleFrom(
+                    backgroundColor: Theme.of(context).colorScheme.primary,
+                    foregroundColor: Colors.white,
                   ),
+                  child: const Text('MiAuthで認証'),
                 ),
-              ),
-            ],
+              ],
+            ),
+          ],
+        ),
+      ),
+    );
+  }
 
-            // ローディング
-            if (_isLoading) ...[
-              const SizedBox(height: 16),
-              const Center(
-                child: CircularProgressIndicator(),
-              ),
+  Widget _buildServerInfoCard() {
+    return Card(
+      child: Padding(
+        padding: const EdgeInsets.all(16.0),
+        child: Column(
+          crossAxisAlignment: CrossAxisAlignment.start,
+          children: [
+            const Text(
+              'サーバー情報',
+              style: TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
+            ),
+            const SizedBox(height: 8),
+            Text('認証エンドポイント:\n${_serverInfo!.authorizationEndpoint}'),
+            const SizedBox(height: 4),
+            Text('トークンエンドポイント:\n${_serverInfo!.tokenEndpoint}'),
+            if (_serverInfo!.scopesSupported != null) ...[
+              const SizedBox(height: 4),
+              Text(
+                  'サポートされているスコープ:\n${_serverInfo!.scopesSupported!.join(', ')}'),
             ],
           ],
         ),
       ),
     );
   }
+
+  Widget _buildServerInfoTab(BuildContext context) {
+    return Column(
+      crossAxisAlignment: CrossAxisAlignment.stretch,
+      children: [
+        Card(
+          child: Padding(
+            padding: const EdgeInsets.all(16.0),
+            child: Column(
+              crossAxisAlignment: CrossAxisAlignment.start,
+              children: [
+                const Text(
+                  'サーバー情報の確認',
+                  style: TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
+                ),
+                const SizedBox(height: 8),
+                TextField(
+                  controller: _hostController,
+                  decoration: const InputDecoration(
+                    labelText: 'ホスト',
+                    hintText: '例: misskey.io',
+                  ),
+                ),
+                const SizedBox(height: 16),
+                ElevatedButton(
+                  onPressed: _checkServerInfo,
+                  child: const Text('サーバー情報を確認'),
+                ),
+              ],
+            ),
+          ),
+        ),
+        if (_serverInfo != null) ...[
+          const SizedBox(height: 16),
+          _buildServerInfoCard(),
+        ],
+      ],
+    );
+  }
+
+  // 画面内のエラーカードは廃止（Snackbarのみ使用）
 }
diff --git a/example/pubspec.yaml b/example/pubspec.yaml
index 062ef77..d2e03ed 100644
--- a/example/pubspec.yaml
+++ b/example/pubspec.yaml
@@ -15,6 +15,7 @@ dependencies:
   misskey_auth:
     path: ../
   http: ^1.1.0
+  loader_overlay: ^3.0.0
 
 dev_dependencies:
   flutter_test:
diff --git a/lib/misskey_auth.dart b/lib/misskey_auth.dart
index 5d6c4ed..d6f9fea 100644
--- a/lib/misskey_auth.dart
+++ b/lib/misskey_auth.dart
@@ -1,8 +1,10 @@
 // Models
 export 'src/models/oauth_models.dart';
+export 'src/models/miauth_models.dart';
 
 // API
 export 'src/api/misskey_oauth_client.dart';
+export 'src/api/misskey_miauth_client.dart';
 
 // Exceptions
 export 'src/exceptions/misskey_auth_exception.dart';
diff --git a/lib/src/api/misskey_miauth_client.dart b/lib/src/api/misskey_miauth_client.dart
new file mode 100644
index 0000000..0287c0b
--- /dev/null
+++ b/lib/src/api/misskey_miauth_client.dart
@@ -0,0 +1,184 @@
+import 'dart:math';
+
+import 'package:dio/dio.dart';
+import 'package:flutter/foundation.dart';
+import 'package:flutter_secure_storage/flutter_secure_storage.dart';
+import 'package:flutter/services.dart';
+import 'package:flutter_web_auth_2/flutter_web_auth_2.dart';
+
+import '../models/miauth_models.dart';
+import '../exceptions/misskey_auth_exception.dart';
+
+/// Misskey の MiAuth 認証を扱うクライアント
+class MisskeyMiAuthClient {
+  final Dio _dio;
+  final FlutterSecureStorage _storage;
+
+  // ストレージキー（OAuth 実装と揃える）
+  static const _accessTokenKey = 'misskey_access_token';
+  static const _hostKey = 'misskey_host';
+
+  MisskeyMiAuthClient({
+    Dio? dio,
+    FlutterSecureStorage? storage,
+  })  : _dio = dio ?? Dio(),
+        _storage = storage ?? const FlutterSecureStorage();
+
+  /// ランダムなセッション ID を生成（URL セーフな英数字）
+  String generateSessionId({int length = 32}) {
+    const charset =
+        'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
+    final random = Random.secure();
+    return List.generate(length, (_) => charset[random.nextInt(charset.length)])
+        .join();
+  }
+
+  /// MiAuth 認証を開始し、成功すればアクセストークンを返す
+  Future<MiAuthTokenResponse> authenticate(MisskeyMiAuthConfig config) async {
+    try {
+      // 1. セッション ID を生成
+      final sessionId = generateSessionId();
+      if (kDebugMode) {
+        print('MiAuth セッション: $sessionId');
+      }
+
+      // 2. 認証 URL を構築
+      final permissions = config.permissions.join(',');
+      final query = <String, String>{
+        'name': config.appName,
+        'callback': config.callbackUrl,
+        if (permissions.isNotEmpty) 'permission': permissions,
+        if (config.iconUrl != null && config.iconUrl!.isNotEmpty)
+          'icon': config.iconUrl!,
+      };
+
+      final authUri = Uri(
+        scheme: 'https',
+        host: config.host,
+        path: '/miauth/$sessionId',
+        queryParameters: query,
+      );
+
+      if (kDebugMode) {
+        print('MiAuth URL: $authUri');
+      }
+
+      // 3. ブラウザで認証ページを開く
+      late final String result;
+      try {
+        result = await FlutterWebAuth2.authenticate(
+          url: authUri.toString(),
+          callbackUrlScheme: config.callbackScheme,
+        );
+      } on PlatformException catch (e) {
+        final code = (e.code).toLowerCase();
+        if (code.contains('cancel')) {
+          throw const UserCancelledException();
+        }
+        if (e.message != null &&
+            e.message!.toLowerCase().contains('callback')) {
+          throw CallbackSchemeErrorException(
+              details: e.message, originalException: e);
+        }
+        throw AuthorizationLaunchException(
+            details: e.message, originalException: e);
+      } catch (e) {
+        if (e is MisskeyAuthException) rethrow;
+        throw AuthorizationLaunchException(details: e.toString());
+      }
+
+      if (kDebugMode) {
+        print('MiAuth コールバック URL: $result');
+      }
+
+      // 4. 許可後にチェック API を叩いてトークンを取得
+      final checkUrl = Uri(
+        scheme: 'https',
+        host: config.host,
+        path: '/api/miauth/$sessionId/check',
+      );
+
+      final response = await _dio.post(
+        checkUrl.toString(),
+        options: Options(contentType: 'application/json'),
+        data: <String, dynamic>{},
+      );
+
+      if (response.statusCode != 200) {
+        final status = response.statusCode;
+        String details = 'status=$status';
+        final data = response.data;
+        if (data is Map<String, dynamic>) {
+          final err = data['error'] ?? data['message'];
+          if (err != null) {
+            details = '$details, $err';
+          }
+        }
+        // セッション不正や期限切れなどをある程度推定
+        if (status == 404 || status == 410) {
+          throw MiAuthSessionInvalidException(details: details);
+        }
+        throw MiAuthCheckFailedException(details: details);
+      }
+
+      final body = response.data as Map<String, dynamic>;
+      final check = MiAuthCheckResponse.fromJson(body);
+
+      if (!check.ok || check.token == null || check.token!.isEmpty) {
+        throw const MiAuthDeniedException();
+      }
+
+      // 5. トークン保存
+      try {
+        await _storage.write(key: _hostKey, value: config.host);
+        await _storage.write(key: _accessTokenKey, value: check.token);
+      } on PlatformException catch (e) {
+        throw SecureStorageException(details: e.message, originalException: e);
+      } catch (e) {
+        if (e is MisskeyAuthException) rethrow;
+        throw SecureStorageException(details: e.toString());
+      }
+
+      if (kDebugMode) {
+        print('MiAuth 成功');
+      }
+      return MiAuthTokenResponse(token: check.token!, user: check.user);
+    } on MisskeyAuthException {
+      rethrow;
+    } on DioException catch (e) {
+      throw NetworkException(details: e.message, originalException: e);
+    } on PlatformException catch (e) {
+      final code = (e.code).toLowerCase();
+      if (code.contains('cancel')) {
+        throw const UserCancelledException();
+      }
+      throw AuthorizationLaunchException(
+          details: e.message, originalException: e);
+    } on FormatException catch (e) {
+      throw ResponseParseException(details: e.message, originalException: e);
+    } catch (e) {
+      if (kDebugMode) {
+        print('MiAuth エラー: $e');
+      }
+      throw MisskeyAuthException('MiAuthでエラーが発生しました', details: e.toString());
+    }
+  }
+
+  /// 保存された MiAuth トークンを取得
+  Future<String?> getStoredAccessToken() async {
+    try {
+      return _storage.read(key: _accessTokenKey);
+    } on PlatformException catch (e) {
+      throw SecureStorageException(details: e.message, originalException: e);
+    }
+  }
+
+  /// MiAuth の保存情報を削除
+  Future<void> clearTokens() async {
+    try {
+      await _storage.deleteAll();
+    } on PlatformException catch (e) {
+      throw SecureStorageException(details: e.message, originalException: e);
+    }
+  }
+}
diff --git a/lib/src/api/misskey_oauth_client.dart b/lib/src/api/misskey_oauth_client.dart
index 74b0912..3880c4a 100644
--- a/lib/src/api/misskey_oauth_client.dart
+++ b/lib/src/api/misskey_oauth_client.dart
@@ -4,8 +4,10 @@ import 'package:crypto/crypto.dart';
 import 'package:dio/dio.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter_secure_storage/flutter_secure_storage.dart';
+import 'package:flutter/services.dart';
 import 'package:flutter_web_auth_2/flutter_web_auth_2.dart';
 import '../models/oauth_models.dart';
+import '../exceptions/misskey_auth_exception.dart';
 
 /// MisskeyのOAuth認証を管理するクライアント
 class MisskeyOAuthClient {
@@ -34,13 +36,24 @@ class MisskeyOAuthClient {
       if (response.statusCode == 200) {
         return OAuthServerInfo.fromJson(response.data);
       }
-      return null;
+      if (response.statusCode == 404 || response.statusCode == 501) {
+        // 非対応と判断
+        return null;
+      }
+      // その他のステータスはサーバー側の問題として扱う
+      throw ServerInfoException('OAuth情報の取得に失敗しました: ${response.statusCode}');
+    } on DioException catch (e) {
+      if (e.response?.statusCode == 404 || e.response?.statusCode == 501) {
+        return null; // 非対応
+      }
+      throw NetworkException(details: e.message, originalException: e);
+    } on FormatException catch (e) {
+      throw ResponseParseException(details: e.message, originalException: e);
     } catch (e) {
-      // OAuth非対応の場合はnullを返す
       if (kDebugMode) {
         print('OAuth情報取得エラー: $e');
       }
-      return null;
+      throw ServerInfoException('OAuth情報の取得に失敗しました: $e');
     }
   }
 
@@ -76,7 +89,7 @@ class MisskeyOAuthClient {
       }
       final serverInfo = await getOAuthServerInfo(config.host);
       if (serverInfo == null) {
-        throw Exception('このサーバーはOAuth認証に対応していません');
+        throw OAuthNotSupportedException(config.host);
       }
       if (kDebugMode) {
         print('認証エンドポイント: ${serverInfo.authorizationEndpoint}');
@@ -123,10 +136,30 @@ class MisskeyOAuthClient {
         print('コールバックURLスキーム: $callbackUrlScheme');
       }
 
-      final result = await FlutterWebAuth2.authenticate(
-        url: authUrl.toString(),
-        callbackUrlScheme: callbackUrlScheme,
-      );
+      late final String result;
+      try {
+        result = await FlutterWebAuth2.authenticate(
+          url: authUrl.toString(),
+          callbackUrlScheme: callbackUrlScheme,
+        );
+      } on PlatformException catch (e) {
+        // FlutterWebAuth2 の代表的なケースをマッピング
+        final code = (e.code).toLowerCase();
+        if (code.contains('cancel')) {
+          throw const UserCancelledException();
+        }
+        // コールバックスキーム不一致/未設定の可能性
+        if (e.message != null &&
+            e.message!.toLowerCase().contains('callback')) {
+          throw CallbackSchemeErrorException(
+              details: e.message, originalException: e);
+        }
+        throw AuthorizationLaunchException(
+            details: e.message, originalException: e);
+      } catch (e) {
+        if (e is MisskeyAuthException) rethrow;
+        throw AuthorizationLaunchException(details: e.toString());
+      }
 
       if (kDebugMode) {
         print('認証結果URL: $result');
@@ -134,6 +167,16 @@ class MisskeyOAuthClient {
 
       // 5. コールバックURLからパラメータを取得
       final uri = Uri.parse(result);
+      // 認可サーバーからのエラー（RFC6749）
+      final authError = uri.queryParameters['error'];
+      if (authError != null && authError.isNotEmpty) {
+        final desc = uri.queryParameters['error_description'];
+        final errMsg = desc == null || desc.isEmpty
+            ? 'error=$authError'
+            : 'error=$authError, description=$desc';
+        throw AuthorizationServerErrorException(details: errMsg);
+      }
+
       final code = uri.queryParameters['code'];
       final returnedState = uri.queryParameters['state'];
 
@@ -144,11 +187,11 @@ class MisskeyOAuthClient {
 
       // 6. stateを検証
       if (returnedState != state) {
-        throw Exception('stateが一致しません');
+        throw const StateMismatchException();
       }
 
       if (code == null) {
-        throw Exception('認証コードが取得できませんでした');
+        throw const AuthorizationCodeMissingException();
       }
 
       // 7. 認証コードをトークンと交換
@@ -165,22 +208,42 @@ class MisskeyOAuthClient {
       );
 
       // 8. トークンを保存
-      await _saveTokens(
-        host: config.host,
-        accessToken: tokenResponse.accessToken,
-        refreshToken: tokenResponse.refreshToken,
-        expiresIn: tokenResponse.expiresIn,
-      );
+      try {
+        await _saveTokens(
+          host: config.host,
+          accessToken: tokenResponse.accessToken,
+          refreshToken: tokenResponse.refreshToken,
+          expiresIn: tokenResponse.expiresIn,
+        );
+      } on PlatformException catch (e) {
+        throw SecureStorageException(details: e.message, originalException: e);
+      } catch (e) {
+        if (e is MisskeyAuthException) rethrow;
+        throw SecureStorageException(details: e.toString());
+      }
 
       if (kDebugMode) {
         print('認証成功！');
       }
       return tokenResponse;
+    } on MisskeyAuthException {
+      rethrow;
+    } on DioException catch (e) {
+      // ネットワーク層の例外
+      throw NetworkException(details: e.message, originalException: e);
+    } on PlatformException catch (e) {
+      final code = (e.code).toLowerCase();
+      if (code.contains('cancel')) {
+        throw const UserCancelledException();
+      }
+      throw AuthorizationLaunchException(
+          details: e.message, originalException: e);
     } catch (e) {
       if (kDebugMode) {
         print('認証エラー: $e');
       }
-      rethrow;
+      // 想定外はベース例外に包む
+      throw MisskeyAuthException(e.toString());
     }
   }
 
@@ -212,14 +275,43 @@ class MisskeyOAuthClient {
       if (response.statusCode == 200) {
         return OAuthTokenResponse.fromJson(response.data);
       }
-      throw Exception('トークン交換に失敗しました: ${response.statusCode}');
-    } catch (e) {
-      if (e is DioException) {
-        if (kDebugMode) {
-          print('DioException: ${e.response?.data}');
+      final status = response.statusCode;
+      String message = 'トークン交換に失敗しました: $status';
+      // RFC準拠のエラーフィールドがあれば詳細に含める
+      final data = response.data;
+      if (data is Map<String, dynamic>) {
+        final err = data['error'];
+        final desc = data['error_description'];
+        if (err != null) {
+          message =
+              '$message (error=$err${desc != null ? ', description=$desc' : ''})';
+        }
+      }
+      throw TokenExchangeException(message);
+    } on DioException catch (e) {
+      if (kDebugMode) {
+        print('DioException: ${e.response?.data}');
+      }
+      if (e.response != null) {
+        final status = e.response?.statusCode;
+        String message = 'トークン交換に失敗しました: $status';
+        final data = e.response?.data;
+        if (data is Map<String, dynamic>) {
+          final err = data['error'];
+          final desc = data['error_description'];
+          if (err != null) {
+            message =
+                '$message (error=$err${desc != null ? ', description=$desc' : ''})';
+          }
         }
+        throw TokenExchangeException(message);
       }
-      throw Exception('トークン交換中にエラーが発生しました: $e');
+      // レスポンスが無い＝ネットワーク層の失敗
+      throw NetworkException(details: e.message, originalException: e);
+    } on FormatException catch (e) {
+      throw ResponseParseException(details: e.message, originalException: e);
+    } catch (e) {
+      throw MisskeyAuthException('トークン交換中にエラーが発生しました', details: e.toString());
     }
   }
 
@@ -246,11 +338,19 @@ class MisskeyOAuthClient {
 
   /// 保存されたアクセストークンを取得
   Future<String?> getStoredAccessToken() async {
-    return await _storage.read(key: _accessTokenKey);
+    try {
+      return await _storage.read(key: _accessTokenKey);
+    } on PlatformException catch (e) {
+      throw SecureStorageException(details: e.message, originalException: e);
+    }
   }
 
   /// トークンをクリア
   Future<void> clearTokens() async {
-    await _storage.deleteAll();
+    try {
+      await _storage.deleteAll();
+    } on PlatformException catch (e) {
+      throw SecureStorageException(details: e.message, originalException: e);
+    }
   }
 }
diff --git a/lib/src/exceptions/misskey_auth_exception.dart b/lib/src/exceptions/misskey_auth_exception.dart
index d495f07..2f3b74b 100644
--- a/lib/src/exceptions/misskey_auth_exception.dart
+++ b/lib/src/exceptions/misskey_auth_exception.dart
@@ -44,3 +44,101 @@ class TokenExchangeException extends MisskeyAuthException {
 class ServerInfoException extends MisskeyAuthException {
   const ServerInfoException(super.message);
 }
+
+/// コールバックURLスキーム（カスタムスキーム）が未設定または不一致の場合の例外
+class CallbackSchemeErrorException extends MisskeyAuthException {
+  const CallbackSchemeErrorException(
+      {String? details, Exception? originalException})
+      : super('The callback URL scheme is not set or does not match.',
+            details: details, originalException: originalException);
+}
+
+/// 認証UI（ブラウザ等）の起動に失敗した場合の例外
+class AuthorizationLaunchException extends MisskeyAuthException {
+  const AuthorizationLaunchException(
+      {String? details, Exception? originalException})
+      : super('Failed to display the authentication screen.',
+            details: details, originalException: originalException);
+}
+
+/// ユーザーが認証をキャンセルした場合の例外
+class UserCancelledException extends MisskeyAuthException {
+  const UserCancelledException({String? details, Exception? originalException})
+      : super('The user canceled the authentication.',
+            details: details, originalException: originalException);
+}
+
+/// ネットワーク層での例外（タイムアウト/オフライン/SSL等）
+class NetworkException extends MisskeyAuthException {
+  const NetworkException({String? details, Exception? originalException})
+      : super('A network error has occurred.',
+            details: details, originalException: originalException);
+}
+
+/// サーバーレスポンスのパースに失敗した場合の例外
+class ResponseParseException extends MisskeyAuthException {
+  const ResponseParseException({String? details, Exception? originalException})
+      : super('Failed to parse the server response.',
+            details: details, originalException: originalException);
+}
+
+/// セキュアストレージの操作に失敗した場合の例外
+class SecureStorageException extends MisskeyAuthException {
+  const SecureStorageException({String? details, Exception? originalException})
+      : super('Failed to operate the secure storage.',
+            details: details, originalException: originalException);
+}
+
+/// OAuthのstate検証に失敗した場合の例外
+class StateMismatchException extends MisskeyAuthException {
+  const StateMismatchException({String? details, Exception? originalException})
+      : super('The state does not match.',
+            details: details, originalException: originalException);
+}
+
+/// OAuthの認可コードが取得できなかった場合の例外
+class AuthorizationCodeMissingException extends MisskeyAuthException {
+  const AuthorizationCodeMissingException(
+      {String? details, Exception? originalException})
+      : super('Failed to get the authorization code.',
+            details: details, originalException: originalException);
+}
+
+/// 認可サーバーがエラーを返した場合（error, error_description など）
+class AuthorizationServerErrorException extends MisskeyAuthException {
+  const AuthorizationServerErrorException(
+      {String? details, Exception? originalException})
+      : super('The authorization server returned an error.',
+            details: details, originalException: originalException);
+}
+
+/// MiAuth がユーザーによって拒否/キャンセルされた場合の例外
+class MiAuthDeniedException extends MisskeyAuthException {
+  const MiAuthDeniedException({String? details, Exception? originalException})
+      : super('MiAuth authentication was canceled/rejected.',
+            details: details, originalException: originalException);
+}
+
+/// MiAuth のチェックAPIが失敗（非200）した場合の例外
+class MiAuthCheckFailedException extends MisskeyAuthException {
+  const MiAuthCheckFailedException(
+      {String? details, Exception? originalException})
+      : super('MiAuth check failed.',
+            details: details, originalException: originalException);
+}
+
+/// MiAuth のセッションが見つからない/期限切れなどで無効な場合の例外
+class MiAuthSessionInvalidException extends MisskeyAuthException {
+  const MiAuthSessionInvalidException(
+      {String? details, Exception? originalException})
+      : super('MiAuth session is invalid or expired.',
+            details: details, originalException: originalException);
+}
+
+/// サーバーが MiAuth に対応していない可能性がある場合の例外（必要に応じて使用）
+class MiAuthNotSupportedException extends MisskeyAuthException {
+  const MiAuthNotSupportedException(
+      {String? details, Exception? originalException})
+      : super('This server may not support MiAuth.',
+            details: details, originalException: originalException);
+}
diff --git a/lib/src/models/auth_config.dart b/lib/src/models/auth_config.dart
deleted file mode 100644
index 83e8d9e..0000000
--- a/lib/src/models/auth_config.dart
+++ /dev/null
@@ -1,76 +0,0 @@
-import '../exceptions/misskey_auth_exception.dart';
-
-/// Misskey認証の設定を表すクラス
-class AuthConfig {
-  /// Misskeyサーバーのホスト（例: misskey.io）
-  final String host;
-
-  /// アプリケーションのクライアントID
-  final String clientId;
-
-  /// アプリケーションのクライアントシークレット
-  final String clientSecret;
-
-  /// 認証完了後のリダイレクトURI
-  final String redirectUri;
-
-  /// 要求するスコープ（カンマ区切り）
-  final String scopes;
-
-  /// アプリケーション名
-  final String appName;
-
-  /// アプリケーションの説明
-  final String? appDescription;
-
-  /// アプリケーションのアイコンURL
-  final String? appIconUrl;
-
-  /// アプリケーションの権限
-  final List<String>? permissions;
-
-  const AuthConfig({
-    required this.host,
-    required this.clientId,
-    required this.clientSecret,
-    required this.redirectUri,
-    this.scopes = 'read:account,write:notes',
-    required this.appName,
-    this.appDescription,
-    this.appIconUrl,
-    this.permissions,
-  });
-
-  /// 設定が有効かどうかを検証する
-  bool get isValid {
-    return host.isNotEmpty &&
-        clientId.isNotEmpty &&
-        clientSecret.isNotEmpty &&
-        redirectUri.isNotEmpty &&
-        appName.isNotEmpty;
-  }
-
-  /// 設定の検証を行い、無効な場合は例外を投げる
-  void validate() {
-    if (!isValid) {
-      throw const InvalidAuthConfigException(
-        '認証設定が無効です。host、clientId、clientSecret、redirectUri、appNameは必須です。',
-      );
-    }
-  }
-
-  /// サーバーのベースURLを取得
-  String get serverUrl {
-    return 'https://$host';
-  }
-
-  /// OAuth認証エンドポイントのURLを取得
-  String get oauthWellKnownUrl {
-    return '$serverUrl/.well-known/oauth-authorization-server';
-  }
-
-  /// MiAuth認証エンドポイントのURLを取得
-  String get miauthUrl {
-    return '$serverUrl/miauth';
-  }
-}
diff --git a/lib/src/models/auth_result.dart b/lib/src/models/auth_result.dart
deleted file mode 100644
index 2875918..0000000
--- a/lib/src/models/auth_result.dart
+++ /dev/null
@@ -1,98 +0,0 @@
-/// Misskey認証の結果を表すクラス
-class AuthResult {
-  /// アクセストークン
-  final String accessToken;
-
-  /// リフレッシュトークン（OAuth認証の場合）
-  final String? refreshToken;
-
-  /// トークンの有効期限（秒）
-  final int? expiresIn;
-
-  /// 認証方式（oauth または miauth）
-  final String authType;
-
-  /// ユーザー情報
-  final Map<String, dynamic>? userInfo;
-
-  /// 認証が成功したかどうか
-  final bool isSuccess;
-
-  /// エラーメッセージ（認証が失敗した場合）
-  final String? errorMessage;
-
-  const AuthResult({
-    required this.accessToken,
-    this.refreshToken,
-    this.expiresIn,
-    required this.authType,
-    this.userInfo,
-    this.isSuccess = true,
-    this.errorMessage,
-  });
-
-  /// 認証失敗時の結果を作成するファクトリメソッド
-  factory AuthResult.failure({
-    required String errorMessage,
-    required String authType,
-  }) {
-    return AuthResult(
-      accessToken: '',
-      authType: authType,
-      isSuccess: false,
-      errorMessage: errorMessage,
-    );
-  }
-
-  /// OAuth認証成功時の結果を作成するファクトリメソッド
-  factory AuthResult.oauthSuccess({
-    required String accessToken,
-    String? refreshToken,
-    int? expiresIn,
-    Map<String, dynamic>? userInfo,
-  }) {
-    return AuthResult(
-      accessToken: accessToken,
-      refreshToken: refreshToken,
-      expiresIn: expiresIn,
-      authType: 'oauth',
-      userInfo: userInfo,
-      isSuccess: true,
-    );
-  }
-
-  /// MiAuth認証成功時の結果を作成するファクトリメソッド
-  factory AuthResult.miauthSuccess({
-    required String accessToken,
-    Map<String, dynamic>? userInfo,
-  }) {
-    return AuthResult(
-      accessToken: accessToken,
-      authType: 'miauth',
-      userInfo: userInfo,
-      isSuccess: true,
-    );
-  }
-
-  /// OAuth認証開始時の結果を作成するファクトリメソッド
-  factory AuthResult.oauthStarted({
-    required String authUrl,
-    required String codeVerifier,
-  }) {
-    return AuthResult(
-      accessToken: '',
-      authType: 'oauth',
-      isSuccess: true,
-      errorMessage: null,
-    );
-  }
-
-  @override
-  String toString() {
-    if (isSuccess) {
-      return 'AuthResult(success: true, type: $authType, token: ${accessToken.substring(0, 10)}...)';
-    } else {
-      return 'AuthResult(success: false, error: $errorMessage)';
-    }
-  }
-}
diff --git a/lib/src/models/miauth_models.dart b/lib/src/models/miauth_models.dart
new file mode 100644
index 0000000..626ef43
--- /dev/null
+++ b/lib/src/models/miauth_models.dart
@@ -0,0 +1,66 @@
+/// MiAuth 認証の設定を表すクラス
+class MisskeyMiAuthConfig {
+  /// Misskey サーバーのホスト（例: misskey.io）
+  final String host;
+
+  /// アプリケーション名（ユーザーに表示）
+  final String appName;
+
+  /// カスタム URL スキーム（例: misskeyauth）
+  final String callbackScheme;
+
+  /// 要求する権限一覧（例: ['read:account', 'write:notes']）
+  final List<String> permissions;
+
+  /// アプリアイコンの URL（任意）
+  final String? iconUrl;
+
+  const MisskeyMiAuthConfig({
+    required this.host,
+    required this.appName,
+    required this.callbackScheme,
+    this.permissions = const <String>[],
+    this.iconUrl,
+  });
+
+  /// コールバック URL（例: misskeyauth://oauth/callback）
+  String get callbackUrl {
+    // スキームのみで十分（iOS/Android ともにスキーム一致で復帰可能）
+    return '$callbackScheme://';
+  }
+}
+
+/// MiAuth チェック API のレスポンス
+class MiAuthCheckResponse {
+  final bool ok;
+  final String? token;
+  final Map<String, dynamic>? user;
+
+  const MiAuthCheckResponse({
+    required this.ok,
+    this.token,
+    this.user,
+  });
+
+  factory MiAuthCheckResponse.fromJson(Map<String, dynamic> json) {
+    return MiAuthCheckResponse(
+      ok: json['ok'] == true,
+      token: json['token'] as String?,
+      user: json['user'] as Map<String, dynamic>?,
+    );
+  }
+}
+
+/// MiAuth 成功時の結果（利用側が扱いやすい形）
+class MiAuthTokenResponse {
+  /// アクセストークン
+  final String token;
+
+  /// 付随するユーザー情報（任意）
+  final Map<String, dynamic>? user;
+
+  const MiAuthTokenResponse({
+    required this.token,
+    this.user,
+  });
+}
diff --git a/lib/src/models/misskey_server_info.dart b/lib/src/models/misskey_server_info.dart
deleted file mode 100644
index 980ef75..0000000
--- a/lib/src/models/misskey_server_info.dart
+++ /dev/null
@@ -1,69 +0,0 @@
-/// Misskeyサーバーの情報を表すクラス
-class MisskeyServerInfo {
-  /// サーバーのホスト
-  final String host;
-
-  /// OAuth 2.0がサポートされているかどうか
-  final bool supportsOAuth;
-
-  /// OAuth認証エンドポイント
-  final String? authorizationEndpoint;
-
-  /// OAuthトークンエンドポイント
-  final String? tokenEndpoint;
-
-  /// サーバーのバージョン情報
-  final String? version;
-
-  /// サーバーの名前
-  final String? name;
-
-  /// サーバーの説明
-  final String? description;
-
-  const MisskeyServerInfo({
-    required this.host,
-    required this.supportsOAuth,
-    this.authorizationEndpoint,
-    this.tokenEndpoint,
-    this.version,
-    this.name,
-    this.description,
-  });
-
-  /// OAuth認証が利用可能かどうかを判定
-  bool get canUseOAuth {
-    return supportsOAuth &&
-        authorizationEndpoint != null &&
-        tokenEndpoint != null;
-  }
-
-  /// サーバー情報をJSONから作成するファクトリメソッド
-  factory MisskeyServerInfo.fromJson(String host, Map<String, dynamic> json) {
-    final hasOAuthEndpoints = json.containsKey('authorization_endpoint') &&
-        json.containsKey('token_endpoint');
-
-    return MisskeyServerInfo(
-      host: host,
-      supportsOAuth: hasOAuthEndpoints,
-      authorizationEndpoint: json['authorization_endpoint'] as String?,
-      tokenEndpoint: json['token_endpoint'] as String?,
-      version: json['version'] as String?,
-      name: json['name'] as String?,
-      description: json['description'] as String?,
-    );
-  }
-
-  /// デフォルトのサーバー情報を作成するファクトリメソッド
-  factory MisskeyServerInfo.defaultInfo(String host) {
-    return MisskeyServerInfo(
-      host: host,
-      supportsOAuth: false,
-    );
-  }
-
-  @override
-  String toString() {
-    return 'MisskeyServerInfo(host: $host, oauth: $supportsOAuth)';
-  }
-}
diff --git a/pubspec.yaml b/pubspec.yaml
index e9616b0..50ed6d7 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -31,7 +31,7 @@ topics:
 # https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html
 # In Windows, build-name is used as the major, minor, and patch parts
 # of the product and file versions while build-number is used as the build suffix.
-version: 0.1.1-beta
+version: 0.1.2-beta
 
 environment:
   sdk: ">=3.5.0 <4.0.0"