diff --git a/jig-core/src/main/resources/templates/assets/package.js b/jig-core/src/main/resources/templates/assets/package.js
index f4662e2b7..6b9c5a994 100644
--- a/jig-core/src/main/resources/templates/assets/package.js
+++ b/jig-core/src/main/resources/templates/assets/package.js
@@ -562,10 +562,14 @@ function renderPackageDiagram(packageFilterFqn, relatedFilterFqn) {
         }
     });
 
-    const addNodeLines = nodeId => {
-        const label = nodeLabelById.get(nodeId);
-        lines.push(`${nodeId}["${escapeMermaidText(label)}"]`);
+    const addNodeLines = (nodeId, parentSubgraphFqn) => {
         const fqn = diagramNodeIdToFqn.get(nodeId);
+        let displayLabel = nodeLabelById.get(nodeId);
+
+        if (displayLabel === fqn && parentSubgraphFqn && fqn.startsWith(`${parentSubgraphFqn}.`)) {
+            displayLabel = fqn.substring(parentSubgraphFqn.length + 1);
+        }
+        lines.push(`${nodeId}["${escapeMermaidText(displayLabel)}"]`);
         const tooltip = fqn ? escapeMermaidText(fqn) : '';
         lines.push(`click ${nodeId} filterPackageDiagram "${tooltip}"`);
         if (fqn && parentFqns.has(fqn)) {
@@ -591,27 +595,27 @@ function renderPackageDiagram(packageFilterFqn, relatedFilterFqn) {
         }
         current.nodes.push(nodeIdByFqn.get(fqn));
     });
-    const renderGroup = (group, isRoot) => {
-        group.nodes.forEach(addNodeLines);
+    const renderGroup = (group, isRoot, parentSubgraphFqnForNodes) => {
+        group.nodes.forEach(nodeId => addNodeLines(nodeId, parentSubgraphFqnForNodes));
         const childKeys = Array.from(group.children.keys()).sort();
         if (isRoot && group.nodes.length === 0 && childKeys.length === 1) {
-            renderGroup(group.children.get(childKeys[0]), false);
+            renderGroup(group.children.get(childKeys[0]), false, parentSubgraphFqnForNodes);
             return;
         }
         childKeys.forEach(key => {
             const child = group.children.get(key);
             const childNodeCount = child.nodes.length + child.children.size;
             if (childNodeCount <= 1) {
-                renderGroup(child, false);
+                renderGroup(child, false, parentSubgraphFqnForNodes);
                 return;
             }
             const groupId = `G${groupIndex++}`;
             lines.push(`subgraph ${groupId}["${escapeMermaidText(child.key)}"]`);
-            renderGroup(child, false);
+            renderGroup(child, false, child.key);
             lines.push('end');
         });
     };
-    renderGroup(rootGroup, true);
+    renderGroup(rootGroup, true, rootGroup.key);
     if (parentFqns.size > 0) {
         lines.push('classDef parentPackage fill:#ffffde,stroke:#aaaa00,stroke-width:2px');
     }
diff --git a/jig-core/src/test/js/package.test.js b/jig-core/src/test/js/package.test.js
index e05b8e709..3d708eb0c 100644
--- a/jig-core/src/test/js/package.test.js
+++ b/jig-core/src/test/js/package.test.js
@@ -679,6 +679,41 @@ test.describe('package.js', () => {
                 const mutual = doc.getElementById('mutual-dependency-list');
                 assert.equal(mutual.children.length > 0, true);
             });
+
+            test('renderPackageDiagram: サブグラフ内のFQNノードラベルが省略される', () => {
+                const doc = setupDocument();
+                const diagram = setupDiagramEnvironment(doc);
+                setPackageData(doc, {
+                    packages: [
+                        {fqn: 'com.example', name: 'example', classCount: 1},
+                        {fqn: 'com.example.domain', name: 'domain', classCount: 1},
+                        {fqn: 'com.example.domain.model', classCount: 1}, // No 'name' property
+                        {fqn: 'com.example.domain.repository', name: 'repository', classCount: 1},
+                        {fqn: 'com.example.service', name: 'service', classCount: 1},
+                    ],
+                    relations: [
+                        {from: 'com.example.domain.model', to: 'com.example.domain.repository'},
+                        {from: 'com.example.service', to: 'com.example.domain'},
+                    ],
+                });
+
+                pkg.setAggregationDepth(0); // Set to no aggregation to ensure full hierarchy is built
+                pkg.renderPackageDiagram(null, null);
+
+                const diagramContent = diagram.textContent;
+
+                // Match subgraph creation for com.example.domain (using regex for groupId)
+                assert.ok(/subgraph G\d+\["com\.example\.domain"]/.test(diagramContent), 'Expected subgraph for com.example.domain');
+
+                // Check for nodes inside this subgraph:
+                // com.example.domain.model (FQN, should be shortened to 'model')
+                assert.ok(/P\d+\["model"]/.test(diagramContent), 'Expected "com.example.domain.model" to be shortened to "model"');
+                // com.example.domain.repository (has 'name', should remain 'repository')
+                assert.ok(/P\d+\["repository"]/.test(diagramContent), 'Expected "com.example.domain.repository" to remain "repository"');
+
+                // Verify that 'com.example.service' is also present and correctly labeled
+                assert.ok(/P\d+\["service"]/.test(diagramContent), 'Expected "com.example.service" to be labeled "service"');
+            });
         });
 
         test.describe('分岐/エラー', () => {