Furthermore, the directional control valve 28 is connected in tandem with respect to the other directional control valves 24 to 27 so that the hydraulic fluid from the second hydraulic pump 11 is supplied to the other directional control valves 24 to 27 with priority over the directional control valve 28, and its feeder passage 39 is also connected to the second parallel passage 43. The second parallel passage 43 includes a load check valve 44 allowing the hydraulic fluid to flow only in the direction toward the directional control valve 28, and a fixed throttle 45 therein. As with the throttle 42, the throttles 18, 45 each have a function of preventing an abrupt change in the actuator speed which will otherwise be caused upon operation of the actuator associated with the upstream directional control valve.