PURPOSE: To reduce a manufacturing cost of a device and improve accuracy, of controlling by dispensing with an adjustment operation of parts which usually requires adjusting.

CONSTITUTION: A flow rate setting control part 30 sends control signals (a) to (d) in accordance with a curvature of a displacement mode to solenoid valves 21 to 24 which have different, opening ratioes every unit time based on deviation detected by means of a deviation detecting part 27. When a displacement rate of a movable shaft 25 reaches a value L, the sending of the control signals (a) to (d) to the solenoid valves 21 to 24 by means of the flow rate setting control part 30 is stopped. A flow rate to be supplied into a cylinder 20 through flow passages 32 and 33 by means of the solenoid valves 21 to 24 is speedily controlled.