To provide a rocking vane type pump actuator having pressure proofness increased up to 25 MPa required for a pendulum type wave power generator, a more reliable seal structure, and manufacturing cost reduced by rationalizing a fixing method for a fixed vane, allowing the use of a ladder operating actuator for a ship having an almost equal displacement volume in common with the wave power generating pump and achieving a smaller size in application to a robot arm hinge actuator.

The rocking vane type pump actuator is formed in a sealing structure for making a rotor side area close to zero on the outside of a ring seal 18 for sealing a rotor side face 19, and the fixed vane has a circular face the same in curvature as a case inner face and is fixed to the case while contacting it at the almost all circular face. Seals are provided at both ends of the circular face for sealing a pressure only tending to the inside thereof and seals are provided at both ends of the face of the fixed vane contacting a rotor outer periphery face for sealing a pressure only tending to the outside thereof.