To improve responsiveness of inclined rolling control of a variable hydraulic pump at the time when a reciprocating pump is changed from an intake side over to a discharge side.

When either one of two hydraulic cylinders 1, 2 advances and one of pilot valves 25 and 26 is changed over, a change-over valve 4 is changed over by pilot pressure, and the retreated hydraulic cylinder turns to be on the advancing side. Simultaneously, the pilot pressure is detected by a pressure switch 31, a cut-off solenoid valve 40 is magnetized and changed over. As the cut-off solenoid valve 40 is changed over by an electric signal, a change-over valve 33 is changed over by pressure oil from a hydraulic pressure source 41, and a piston 32a of a cylinder 32 for change of an inclined rolling angle is moved in a direction of small inclined rolling. Consequently, inclined rolling of a variable hydraulic pump 5 is controlled in good timing, discharge is reduced, and the piston 3 on the advance side is moved to advance at a low speed.