diff --git a/src/main/java/info/istlab/ServerTester/Host.java b/src/main/java/info/istlab/ServerTester/Host.java
index e47fc88..90c1240 100644
--- a/src/main/java/info/istlab/ServerTester/Host.java
+++ b/src/main/java/info/istlab/ServerTester/Host.java
@@ -19,7 +19,16 @@
     public Host() {
         setTitle("サーバ管理ウィンドウ");
         setSize(300, 200);
-        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+        setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
+        addWindowListener(new java.awt.event.WindowAdapter() {
+            @Override
+            public void windowClosing(java.awt.event.WindowEvent windowEvent) {
+                if (multicastReceiver != null){
+                    multicastReceiver.sender.sendnofity();
+                }
+                System.exit(0);
+            }
+        });
         setVisible(true);
         setupMenu();
         mainPanel = new JPanel();
diff --git a/src/main/java/info/istlab/ServerTester/MulticastSender.java b/src/main/java/info/istlab/ServerTester/MulticastSender.java
index 7059725..a485fed 100644
--- a/src/main/java/info/istlab/ServerTester/MulticastSender.java
+++ b/src/main/java/info/istlab/ServerTester/MulticastSender.java
@@ -67,4 +67,15 @@
         return sb.toString();
     }
 
+    public void sendnofity() {
+        String message = "";
+        byte[] data = message.getBytes();
+        DatagramPacket packet = new DatagramPacket(data, data.length, group, port);
+        try {
+            socket.send(packet);
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+
 }