A sealing ring is provided between an end plate of an eccentric rotation body and a support plate so that a pressure of fluid at high pressure is allowed to work on the end plate, thereby allowing an axial-direction pressing force to work on the end plate. The sealing ring is arranged eccentrically away from a center of a cylinder as forming the eccentric rotation body to minimize separation of the axial-direction pressing force from a thrust load in a radial direction in the end plate thereby reducing turnover moment effectively.