diff --git a/TIASshot/Form1.cs b/TIASshot/Form1.cs
index ed7eae3..1f46ba2 100644
--- a/TIASshot/Form1.cs
+++ b/TIASshot/Form1.cs
@@ -172,6 +172,7 @@
         }
 
         private void btnLightSW_Click(object sender, EventArgs e) {
+            if (!_light.IsOpen) return;
             if (_isLightOn) {
                 _light.TurnOff();
                 btnLightSW.Text = "照明 ON";