PURPOSE: To reduce the pulsation by installing a bridge circuit into a hydraulic circuit and convert the discharge liquid which is generated at the ports of a hydraulic cylinder by the reciprocating movement of a pneumatic piston by the supply of the pressurized air by the switching operation of a selector valve, to a single output.

CONSTITUTION: A pneumatic pressure piston 3 having the equal pressure receiving areas in the both directions is moved in reciprocation by the switching operation of a selector valve 14, and the pressure receiving area in the both directions of a hydraulic piston 8 is made equal, and the discharge quantity supplied from the ports 12 and 13 is made equal and the speed in advance and retreat movement is made equal. The intermittent discharge liquid alternately generated at the ports 12 and 13 is convert to the single output by a bridge circuit 25, and the pressure pulsation can be eliminated.