of the peripheral end portion is lowered from the hub portion 32 by one stage and supports a hard disk a plurality of rotor magnets 60 are fixedly attached to an inner peripheral wall of the circular ring portion 33 at equal intervals the rotor magnets 60 are arranged such that positions of magnetic centers of the rotor magnets 60 in the axial direction are the same as that of a magnetic center of the stator coil 40 and are urged by a rotational magnetic field formed by the stator coil 40 fig2 is a sectional view of essential portions showing a contact state of the shaft portion 31 of the hub shaft 30 and the bearing ring 52 of the motor according to the embodiment as shown in fig2 the bearing ring 52 is formed in a shape of a circular cylinder formed with an inner hollow or vacant portion in a shape of a regular hexagonal cylinder penetrating in the axial direction and an inner peripheral face of the inner vacant portion is formed in a shape in which six planes are connected by side edges of the respective planes portions connecting the side edges of the respective planes form edge portions of an inner peripheral face portion of the inner vacant portion the fixedly attached portion 31 b of the shaft portion 31 of the hub shaft 30 is inserted into the inner vacant portion of the bearing ring 52 and is fixed coaxially with the inner vacant portion thereby substantially central portions among contiguous ones of the edge portions in the inner peripheral face portion of the bearing ring 52 are brought into contact with an outer peripheral face portion of the fixedly attached portion over an entire length along the axial.