To prevent increase in a load of a driving source which drives a pump, with excellent responsiveness, and to effectively decrease energy consumption, in an oil pressure rotary machine.

A pump unit includes: a hydraulic pump 74 (82); a servo mechanism 92 (96) controlling a swash plate angle of a movable swash plate 90 of the hydraulic pump 74 (82); and a piston movement regulating mechanism 248 regulating increase of the swash plate angle of the movable swash plate 90. The piston movement regulating mechanism 248 includes: an outside cylinder 258; a control piston 252 which is slidably provided in an axial direction inside the outside cylinder 258 and whose one end faces an axial end face of a servo piston 100; and a pressure introducing path 256 which introduces operating oil pressure to the other end side of the control piston 252 such that the control piston 252 approaches the servo piston 100 against biasing force of a control spring 254.