Pressure compensating valves disposed at inlet sides of directional control valves are each configured with a step-shaped spool having a larger diameter portion and smaller diameter portions and pressure receiving chambers are provided to sandwich the larger diameter portion such that a pump delivery pressure and an inlet pressure of a metering throttle of the directional control valve acts in the chambers, respectively, and further pressure receiving chambers are provided at respective ends of the smaller diameter portions such that an outlet pressure of the metering throttle and a signal pressure act in the chambers, respectively. A check valve operated by the outlet pressure of the metering throttle is fitted in the smaller diameter end portion positioned on the side of the pressure receiving chamber to reduce the pump delivery pressure and produce a signal pressure. A sleeve having opposed ends positioned in a pressure receiving chamber in which the outlet pressure of the metering throttle is introduced and in the pressure receiving chamber is fitted on the smaller diameter portion, and the outlet pressure of the metering throttle is introduced to the pressure receiving chamber by movement of the sleeve.