To surely prevent impact and revolving swing of an upper revolving superstructure in start and stop of a working mechanism in a very inexpensive constitution in a construction machine movable in right and left directions to the upper revolving superstructure.

The movement operation of an offset cylinder 10 is detected by a potentiometer 23, an instruction signal is output to a solenoid valve 26 from a controller 24, brake releasing oil pressure releasing a revolving shaft brake 25c of the upper revolving superstructure is directed from the solenoid valve 26, and when the offset cylinder 10 is stopped, the revolving swing applied on the upper revolving superstructure is suppressed by a reverse revolving prevention valve 41.