PURPOSE: To improve the responsiveness by starting a regulator according to an output signal of a pilot operation mechanism in a hydraulic control circuit which controls a variable pump discharge pressure according to an actuator load.

CONSTITUTION: Changeover valves 1, 2, each being a pilot type, have pilot chambers 1a to 2b respectively connected to pilot operation mechanisms 10, 11. Changeover directions of the changeover valves 1, 2 are specified according to operation directions of operation levers 12, 13, and a pilot rate is controlled according to the operation rate. The maximum value of a pilot pressure obtained by the operation of the levers 13, 14 is selected by means of shuttle valves 14 to 16, and applied to pilot chambers 17a, 17b of a throttle 17. The pressure inside the pilot chamber 17a is lowered compared to that inside the pilot chamber 17b by the pressure loss rate of a throttle 18, and the throttle valve 17 is opened. The valve opening rate is determined based on the operation rates of the pilot operation mechanisms 10, 11. A regulator is driven by the operation of the pilot operation mechanisms, accordingly, and the responsiveness is improved.