Abstract: A hydraulic drive unit of a press machine and a swash plate type variable capacity axial piston pump to use for a hydraulic drive unit. Discharge of the pump and the direction of the hydraulic pressure can be controlled at high speed, and the direction of the hydraulic pressure and the timing of the discharge can coincide. The selector device 12 that includes spool valves in parallel is used in place of a servo valve. An electric motor 30 for driving the pump and cam of the axial piston pump 11 and an electric motor 47 for driving the selector cam of the selector device 12 are controlled cooperatively by commands from the numerical control device 14. Two spools 44a, 44b of the selector device 12 perform changeover actuation alternately. Synchronous control of the discharge of the axial piston pump 11 and the flowing direction change of working fluid to the hydraulic pressure cylinder 1 are done, so that the piston 1a of the hydraulic pressure cylinder 1 is made to move up and down.