diff --git a/IteratorTasks.Extensions/IteratorTasks.Extensions.csproj b/IteratorTasks.Extensions/IteratorTasks.Extensions.csproj
index 516035b..7c2e882 100644
--- a/IteratorTasks.Extensions/IteratorTasks.Extensions.csproj
+++ b/IteratorTasks.Extensions/IteratorTasks.Extensions.csproj
@@ -43,6 +43,7 @@
     <Compile Include="TaskEx.cs" />
     <Compile Include="TaskExtensions.cs" />
     <Compile Include="TaskUtility.cs" />
+    <Compile Include="TaskUtility_Success.cs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\IteratorTasks\IteratorTasks.csproj">
diff --git a/IteratorTasks.Extensions/TaskUtility.cs b/IteratorTasks.Extensions/TaskUtility.cs
index c9923b6..aa36e15 100644
--- a/IteratorTasks.Extensions/TaskUtility.cs
+++ b/IteratorTasks.Extensions/TaskUtility.cs
@@ -11,7 +11,7 @@ namespace IteratorTasks
     /// 特に、タイマー関連は、マルチスレッドになってしまうので Unity とは相性よくないかも。
     /// Unity は yield return new WaitForSeconds(t); とか使ってほしそうだし。
     /// </remarks>
-    public static class TaskUtility
+    public static partial class TaskUtility
     {
         /// <summary>
         /// 二重起動防止付きのタスク生成関数を返す。
diff --git a/IteratorTasks.Extensions/TaskUtility_Success.cs b/IteratorTasks.Extensions/TaskUtility_Success.cs
new file mode 100644
index 0000000..cdba738
--- /dev/null
+++ b/IteratorTasks.Extensions/TaskUtility_Success.cs
@@ -0,0 +1,72 @@
+using System;
+
+namespace IteratorTasks
+{
+    public static partial class TaskUtility
+    {
+
+        public static Task OnSuccess(this Task t, Action succesHandler)
+        {
+            return t.ContinueWith(x =>
+            {
+                succesHandler();
+            }, true);
+        }
+
+        public static Task OnSuccess<T>(this Task<T> t, Action<T> succesHandler)
+        {
+            return t.ContinueWith(x =>
+            {
+                succesHandler(t.Result);
+            }, true);
+        }
+
+        public static Task<T> OnSuccess<T>(this Task t, Func<T> succesHandler)
+        {
+            return t.ContinueWith<T>(x =>
+            {
+                return succesHandler();
+            }, true);
+        }
+
+        public static Task<U> OnSuccess<T, U>(this Task<T> t, Func<T, U> succesHandler)
+        {
+            return t.ContinueWith<U>(x =>
+            {
+                return succesHandler(t.Result);
+            }, true);
+        }
+
+        public static Task OnSuccessWithTask(this Task t, Func<Task> succesHandler)
+        {
+            return t.ContinueWithTask(x =>
+            {
+                return succesHandler();
+            }, true);
+        }
+
+        public static Task OnSuccessWithTask<T>(this Task<T> t, Func<T, Task> succesHandler)
+        {
+            return t.ContinueWithTask(x =>
+            {
+                return succesHandler(t.Result);
+            }, true);
+        }
+
+        public static Task<T> OnSuccessWithTask<T>(this Task t, Func<Task<T>> succesHandler)
+        {
+            return t.ContinueWithTask<T>(x =>
+            {
+                return succesHandler();
+            }, true);
+        }
+
+        public static Task<U> OnSuccessWithTask<T, U>(this Task<T> t, Func<T, Task<U>> succesHandler)
+        {
+            return t.ContinueWithTask<U>(x =>
+            {
+                return succesHandler(t.Result);
+            }, true);
+        }
+    }
+}