On the above shown asking popup window on Mac, how can I select another button (left button) by using keyboard. Without clicking mouse button, I want to make left button highlighten. Is there any shortcuts?
After reading Tricon's answer, I got the way!!!
Just see the following shortcuts.
Preferences -> Keyboard -> Keyboard & keyboard input (I don't know the correct English menu, I'm using Korean "탭이 초점을 이동하는 방식 변경 (^F7) )
Once you do ^F7 (In case of mac book, Control + fn + F7) on a popup window, you can travel over buttons on any popup windw!!!
Thank you Tricon for giving me clue :)