diff --git a/mainwindow.cpp b/mainwindow.cpp
--- a/mainwindow.cpp
+++ b/mainwindow.cpp
@@ -57,6 +57,10 @@ MainWindow::MainWindow(QWidget *parent) 
 
 MainWindow::~MainWindow()
 {
+    if (serialPort.isOpen())
+    {
+        serialPort.close();
+    }
     delete ui;
 }