diff --git a/src/main/java/info/istlab/ServerTester/MulticastReceiver.java b/src/main/java/info/istlab/ServerTester/MulticastReceiver.java
index 3564cd3..3ec27d7 100644
--- a/src/main/java/info/istlab/ServerTester/MulticastReceiver.java
+++ b/src/main/java/info/istlab/ServerTester/MulticastReceiver.java
@@ -59,12 +59,8 @@
     }
 
     public void openWindow() {
-        // if (receivedData.size() == 0) {
-        //     JOptionPane.showMessageDialog(Host.mainhost, "受信したデータがありません。", "受信データなし", JOptionPane.WARNING_MESSAGE);
-        //     return;
-        // }
         if (remoteHostsWindow != null) {
-            remoteHostsWindow.setVisible(true);
+            remoteHostsWindow.frame.setVisible(true);
         } else {
             remoteHostsWindow = new RemoteHostsWindow(receivedData);
         }
diff --git a/src/main/java/info/istlab/ServerTester/RemoteHostsWindow.java b/src/main/java/info/istlab/ServerTester/RemoteHostsWindow.java
index daefe63..988e211 100644
--- a/src/main/java/info/istlab/ServerTester/RemoteHostsWindow.java
+++ b/src/main/java/info/istlab/ServerTester/RemoteHostsWindow.java
@@ -23,7 +23,13 @@
         frame = new JFrame();
         frame.setTitle("Remote Hosts");
         frame.setSize(300, 200);
-        frame.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);
+        frame.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
+        frame.addWindowListener(new java.awt.event.WindowAdapter() {
+            @Override
+            public void windowClosing(java.awt.event.WindowEvent windowEvent) {
+                frame.setVisible(false);
+            }
+        });
 
         tabbedPane = new JTabbedPane();
         frame.getContentPane().add(tabbedPane);