diff --git a/Assets/AsmdefHelper/CustomCreate/Editor/AsmdefCustomCreateView.cs b/Assets/AsmdefHelper/CustomCreate/Editor/AsmdefCustomCreateView.cs
index 54ba989..b472443 100644
--- a/Assets/AsmdefHelper/CustomCreate/Editor/AsmdefCustomCreateView.cs
+++ b/Assets/AsmdefHelper/CustomCreate/Editor/AsmdefCustomCreateView.cs
@@ -29,7 +29,11 @@ namespace AsmdefHelper.CustomCreate.Editor {
                         "Packages/dev.n5y.asmdefhelper/AsmdefHelper/CustomCreate/Editor/AsmdefCustomCreateView.uxml");
             }
 
+#if UNITY_2020_1_OR_NEWER
             VisualElement labelFromUXML = visualTree.Instantiate();
+#else
+            VisualElement labelFromUXML = visualTree.CloneTree();
+#endif
             root.Add(labelFromUXML);
 
             // UI取得
diff --git a/Assets/AsmdefHelper/CustomCreate/Editor/AsmdefRenameView.cs b/Assets/AsmdefHelper/CustomCreate/Editor/AsmdefRenameView.cs
index 8665f26..440dd3c 100644
--- a/Assets/AsmdefHelper/CustomCreate/Editor/AsmdefRenameView.cs
+++ b/Assets/AsmdefHelper/CustomCreate/Editor/AsmdefRenameView.cs
@@ -40,7 +40,11 @@ namespace AsmdefHelper.CustomCreate.Editor {
                         "Packages/dev.n5y.asmdefhelper/AsmdefHelper/CustomCreate/Editor/AsmdefRenameView.uxml");
             }
 
+#if UNITY_2020_1_OR_NEWER
             VisualElement labelFromUXML = visualTree.Instantiate();
+#else
+            VisualElement labelFromUXML = visualTree.CloneTree();
+#endif
             root.Add(labelFromUXML);
 
             // UI取得
diff --git a/Assets/AsmdefHelper/DependencyGraph/Editor/AsmdefSelectionView/AsmdefSelectionView.cs b/Assets/AsmdefHelper/DependencyGraph/Editor/AsmdefSelectionView/AsmdefSelectionView.cs
index bf92745..216f468 100644
--- a/Assets/AsmdefHelper/DependencyGraph/Editor/AsmdefSelectionView/AsmdefSelectionView.cs
+++ b/Assets/AsmdefHelper/DependencyGraph/Editor/AsmdefSelectionView/AsmdefSelectionView.cs
@@ -33,7 +33,11 @@ namespace AsmdefHelper.DependencyGraph.Editor {
                         "Packages/dev.n5y.asmdefhelper/AsmdefHelper/DependencyGraph/Editor/AsmdefSelectionView/AsmdefSelectionView.uxml");
             }
 
+#if UNITY_2020_1_OR_NEWER
             VisualElement labelFromUXML = visualTree.Instantiate();
+#else
+            VisualElement labelFromUXML = visualTree.CloneTree();
+#endif
             root.Add(labelFromUXML);
         }
 
diff --git a/Assets/AsmdefHelper/Unity.InternalAPIEditorBridgeDev.001/InspectorWindowWrapper.cs b/Assets/AsmdefHelper/Unity.InternalAPIEditorBridgeDev.001/InspectorWindowWrapper.cs
index 9b71544..afbe10c 100644
--- a/Assets/AsmdefHelper/Unity.InternalAPIEditorBridgeDev.001/InspectorWindowWrapper.cs
+++ b/Assets/AsmdefHelper/Unity.InternalAPIEditorBridgeDev.001/InspectorWindowWrapper.cs
@@ -17,7 +17,11 @@ namespace AsmdefHelper.UnityInternal {
 
         public void AllApply() {
             foreach (var editor in inspectorWindow.tracker.activeEditors) {
+#if UNITY_2021_1_OR_NEWER
                 var assetImporterEditor = editor as UnityEditor.AssetImporters.AssetImporterEditor;
+#else
+                var assetImporterEditor = editor as UnityEditor.Experimental.AssetImporters.AssetImporterEditor;
+#endif
 
                 if (assetImporterEditor != null && assetImporterEditor.HasModified()) {
                     assetImporterEditor.ApplyAndImport();