diff --git a/src/main/java/info/istlab/ServerTester/App.java b/src/main/java/info/istlab/ServerTester/App.java
index 0358bc6..2e36933 100644
--- a/src/main/java/info/istlab/ServerTester/App.java
+++ b/src/main/java/info/istlab/ServerTester/App.java
@@ -27,6 +27,10 @@
 
         // ネットワークインタフェースの調査と選択
         primaryInterface = NetworkInterfaceSelector.getPrimaryInterface();
+        if (primaryInterface == null) {
+            System.out.println("ネットワークインタフェースが見つかりませんでした。");
+            System.exit(1);
+        }
         primaryInetAddr = NetworkInterfaceSelector.getPrimaryInetAddr(primaryInterface);
 
         Host myhost = new Host();
diff --git a/src/main/java/info/istlab/ServerTester/NetworkInterfaceSelector.java b/src/main/java/info/istlab/ServerTester/NetworkInterfaceSelector.java
index a6fb7e5..1737e45 100644
--- a/src/main/java/info/istlab/ServerTester/NetworkInterfaceSelector.java
+++ b/src/main/java/info/istlab/ServerTester/NetworkInterfaceSelector.java
@@ -76,7 +76,10 @@
     }
 
     public NetworkInterface getSelectedInterface() {
-        return selectedInterface;
+        if (showDialog()) {
+            return selectedInterface;
+        }
+        return null;
     }
 
     public static ArrayList<NetworkInterface> getIPv4Interfaces() {