A suction ring is fixed to a motor base and is provided with an outer circumferential section having a first outer diameter that is smaller than an inner diameter of a wall section of the motor base. A plurality of protruded sections each have a second outer diameter larger than the inner diameter of the wall section of the motor base and protrudes outward in a radial direction from the outer circumferential section of the suction ring. The plurality of protruded sections of the suction ring are press fitted into a wall section of the motor base and secures the suction ring to the motor base. One surface of the suction ring coincides with a bottom surface of the ring magnet covering a whole range of a projected area of the ring magnet that is projected onto the surface of the suction ring.