To automatically correct discrepancy of a return position generated in a control valve mechanism by an ambient temperature and an error of manufacture.

In a hydraulic cylinder 3, pressure oil from a hydraulic pressure source 1 is supplied/discharged through a spool valve 6, also a rod 3C is slide displaced. A spool 13 of the spool valve 6 is slide displaced by an electromagnetic actuator 16, it is controlled by a controller 17 comprising a proportional arithmetic circuit, integration arithmetic circuit, compensation arithmetic circuit, etc. In the controller 17, a target value setter 26 and a position detection sensor 27 detecting a position of the rod 3C are connected, the controller 17 feedback controls the hydraulic cylinder 3 so that a target value from the target value setter 26 and a detection value from the position detection sensor 27 are conformed.