To easily achieve the highly accurate positioning of rotor magnets in the axial direction to a rotor hub during manufacture, and to prevent high power consumption arising from a bad effect that is caused to occur to the characteristics of a motor by the flow of a large amount of magnetic flux by the rotor magnets in magnetic shield.

An annular magnetic shield 18c that extends outside in the radial direction is provided at the midway position in the axial direction of the outside circumferential part of the rotor hub 18 made of a ferromagnetic material. A hard disc HD is fixed and supported on a hard-disc supporter 18d at the upper side of the magnetic shield 18c. An annular protruding stripe 18g protrudes downward around the axial line of the rotor hub 18, and is formed inside in the radial direction at the lower side of the magnetic shield 18c. The annular rotor magnets 20 magnetized in the radial direction are fitted and fixed to the outside of the rotor hub 18. The bottom end of the annular portion of the annular protruding stripe 18g of the magnetic shield 18c is made to contact a magnetically neutral portion between S pole and N pole in the radial direction of the upper surface of the rotor magnet 20.