To acculately control an inclination angle of a pump in spite of pressure change of pump line by controlling the inclination angle of a variable displacement hydraulic pump to be a target angle based on an instruction signal value of the inclination angle, a real measured value of the inclination angle and the discharge pressure.

Signal 9 is corrected in a feedforward manner by converting the pressure variation of a pump line 5 to the variable quantity of spool position for making zero of pressure flow to an oil chamber 4 by a correction computing part 17. When the inclination angle of the pump 1 reaches a target inclination angle θref and difference Δθ becomes zero a solenoid valve 7 returns to a spool state where rising portion of pressure Ps of the pump line 5 is corrected and the feed/exhaust of pressure oil to the oil chamber 4 is not executed. As a result, the inclination angle of the pump 1 is stable without being influenced by the pressure of the pump line 5 and response is quick owing to the feedforward correction of the influence of pressure variation.