To reduce a reciprocating motion by applying a pressure in a control flow pipe to act at fixed force in one side end surface of a spool, in a device having a control valve, in which the control valve has a spool, connecting a low pressure connection part alternately to a pressure source or a low pressure source, and connected to a piston cylinder device through the control flow pipe.

A piston cylinder device 2, 6, 7 is provided, this device has a low pressure side 3 provided with a low pressure connection part 8, high pressure side 4 provided with a high pressure connection part 9 and a supply connection part 12 and a pressure intensifier piston 2 constituted as a differential piston between the low/high pressure sides, and has a control valve 14, this control valve has a spool 17, the low pressure connection part 8 is connected alternately to a pressure source P or a low pressure source T, to be connected to the piston cylinder device through a control flow pipe 19, and a high delivery amount in a pressure intensifier 1 for the fluid of which pressure in the control flow pipe 19 is applied to one side of the spool 17, particulary operating fluid, can be attained.