Abstract: When a first rotating shaft is rotationally driven, it rotates a first cylinder barrel splined thereto, and a second cylinder barrel and a valve block united with the first cylinder barrel. In accordance with these rotations, first pistons in first cylinders slide circumferentially on the inclined face of a first swash plate so that they are reciprocated axially in the first cylinder barrel, and second pistons in second cylinders slide circumferentially on the inclined face of a second swash plate so that they are reciprocated axially in the second cylinder barrel. Simultaneously with these reciprocations, a first change-over valve is switched in accordance with the rotations of the first rotating shaft, and a second change-over valve is switched in accordance with the relative rotations of the first rotating shaft and the second rotating shaft.