A vane pump used as a fluid pressure source includes: a rotor that is rotationally driven; a plurality of vanes that are inserted into the rotor in a freely slidable manner; a cam ring at which tip-end portions of the vanes slides as the rotor rotates; a pump chamber that is defined between the adjacent vanes; a suction port that guides working fluid to the pump chamber; a discharge port through which the working fluid discharged from the pump chamber is guided; a groove-like notch that extends from an opening edge of the discharge port in an opposite direction from rotation direction of the rotor, and the notch has a gradient-changing portion at which a rate of change of opening area is decreased in the rotation direction of the rotor.