Question

I usually leave office at 6pm or i leave office usually at 6pm

Answer 1

Ur answer is..........................
I leave office usually at 6 pm

Answer 2

I leave the office usually at 6 pm.

This is because usually is the adverb which is describing the time which is 6 pm and not the fact that he leaves the office.

He leaves the office daily but the time at which he leaves the office is usually 6 pm is what he wants to convey.