Main Menu Bar doesn't show up in OS X

CroCo

I've created simple QMainWindow application in mac. I've added File->new, File->save, and Help. Running the application, the menu doesn't show up. It shows the following

0_1515829018459_Untitled 2.png

This is the designer form

macOS High Sierra Version 10.13.2
Qt Creator 4.3.1
Based on Qt 5.9.1 (Clang 7.0 (Apple), 64 bit)

kenchan

This is a Mac so the main menu is at top of the screen in the common menu. Usually it does not sit on top of of the app window.