diff --git a/src/UniTask/Assets/Plugins/UniTask/Runtime/UniTask.Delay.cs b/src/UniTask/Assets/Plugins/UniTask/Runtime/UniTask.Delay.cs
index fd13bd2..3105d9f 100644
--- a/src/UniTask/Assets/Plugins/UniTask/Runtime/UniTask.Delay.cs
+++ b/src/UniTask/Assets/Plugins/UniTask/Runtime/UniTask.Delay.cs
@@ -106,6 +106,14 @@ namespace Cysharp.Threading.Tasks
                 throw new ArgumentOutOfRangeException("Delay does not allow minus delayTimeSpan. delayTimeSpan:" + delayTimeSpan);
             }
 
+#if UNITY_EDITOR
+            // force use Realtime.
+            if (!UnityEditor.EditorApplication.isPlaying)
+            {
+                delayType = DelayType.Realtime;
+            }
+#endif
+
             switch (delayType)
             {
                 case DelayType.UnscaledDeltaTime: