To easily perform operation by reducing operation force of an operation lever.

A crane is provided with a hydraulic actuator 16, and a directional control valve 20 of the hydraulic actuator operated by the operation lever 18. The directional control valve 20 of the hydraulic actuator 16 is provided with a pilot piston 22 and solenoid valves 24 and 25 for actuating a main spool 21, and a position detector 23 for detecting displacement of the main spool 21, and is provided with an arithmetic operation part 40 for transmitting a control signal to the solenoid valves 24 and 25 by determining a required control quantity for supplementally actuating the pilot piston 22 so as to reduce actuating directional operation force of the main spool 21 of the operation lever 18 on the basis of detecting data of the position detector 23.