A rotating pump includes an outer rotor and an inner rotor. The inner and outer rotors are rotated by a drive shaft between a first side plate and a second side plate to pump put fluid. The first side plate faces the inner and outer rotors and has a first surface and a second surface. The first surface is inclined to an axial direction of the drive shaft to create a wedge-shaped gap between itself and one of the inner and outer rotor. The second surface extends more parallel to a direction perpendicular to the axis direction of the drive shaft than the first surface does. The geometric configurations of the first and second surfaces serve to minimize the leakage of the brake fluid without sacrificing a reduction in resistance to sliding motion of the inner rotor and the outer rotor on the second side plate.