PURPOSE: To realize a moderate responsiveness corresponding to the sense of an operator while making the so-called positive control as a base and taking an actual actuator load pressure into consideration.

CONSTITUTION: A control valve 14 is installed between a variable displacement type hydraulic pump 10 and a hydraulic cylinder 16. This control valve 14 controls a hydraulic oil supply flow rate to the hydraulic cylinder 16 corresponding to the manipulated variable of a lever 22. The controller 30 increases the delivery amount of the hydraulic pump 10 in accordance with the increase of the manipulated variable, while such control is carried out that the delivery amount is restrained as the delivery pressure (p) of this hydraulic pump 10 is higher.