To solve the problem of the deterioration of turning performance caused by a large size and the heavy weight of an entire axle driving device caused by the inevitable installation of an inclined rolling cylinder and the like, in a conventional variable capacity type hydraulic motor comprising a swash plate control mechanism for controlling an inclined rolling angle of a movable swash plate.

A swash plate control mechanism 20 is driven by a turning force transmitted from a steering wheel or a turning operation tool via a link mechanism 110. The swash plate control mechanism 20 is configured for generating the moment around the inclined rolling center 23a exerted to a movable swash plate M1a on the inclined rolling angle increase side at the time of turning by providing the inclined rolling center 23a of the movable swash plate M1a eccentrically from the motor shaft center 6b. Furthermore, a line of the action 87a of a piston synthesized force 87 of a pressing force component 85 applied on the movable swash plate M1a from a sliding piston 81 passes the inclined rolling center 23a of the movable swash plate M1a in a maximum inclined rolling position of the movable swash plate M1a.