A control circuit (91) for rotation is separately placed from a fluid pressure actuator control circuit (25). In the control circuit (91) for rotation, a pump/motor (95) for rotation is connected to closed circuits (92, 93) of a rotation motor (4swh) via a solenoid valve (94) as a directional control valve. A motor/generator (96) for rotation is connected to the pump/motor (95). The motor/generator (96) for rotation is connected to an electric accumulator (23) of a hybrid drive device (10). A path (97) for communication to the outside of a system is led out from piping between the pump/motor (95) for rotation and the solenoid valve (94), and the path (97) feeds operation fluid to fluid pressure actuators of a lower traveling body and a working device. A connection path solenoid valve (98)is provided in the path (97). Fluid pressure energy produced in a rotation system can be directly fed to the outside of the rotation system.