To easily restart operation of a machine body when a key switch is turned on once again even if the key switch is turned off to stop an engine during a working period of time.

There are provided a key switch 2 for starting or stopping the engine 1, a turning motor 5, a turning brake 6, an electromagnetic valve 7 for controlling the turning brake 6, a controller 13, a cord number input device 14, and a timer 17. When the key switch 2 is turned off during a predetermined working period of time, a braked state of the turning brake 6 is released only by turning on the key switch 2 thereafter. On the contrary, when the key switch 2 is turned off except during the working period of time, the braked state of the turning brake 6 is released only when the key switch 2 is turned on thereafter and beside a predetermined code number is input.