A pump discharge amount is divided in accordance with switch amounts of respective switch valves by leading load pressures of actuators to which compensator valves are connected to respective first pressure chambers of the compensator valves, leading a maximum load pressure selected by a selection unit to respective second pressure chambers of the compensator valves, and controlling respective openings of the compensator valves in accordance with respective pressure actions between the respective pressure chambers. A drain passage is provided to connect the first pressure chamber of the compensator valve to a tank, and a flow dividing ratio modification valve is provided to control a pressure in the first pressure chamber.