A rotor 14 is rotatably disposed around a stator 13 that is provided with a plurality of magnetic poles 13a. The inner circumferential face of a rotor frame 14b of the rotor is provided with a magnet 15 magnetized to have alternately opposite polarities in a direction opposing the stator, and magnetized to have alternately opposite polarities in a direction opposing a substrate. The outer circumferential ends of the magnetic poles of the stator are provided with a first extended portion 13c that extends from a magnetic pole base 13d to a substrate 11 side, and a second extended portion 13b that extends from the magnetic pole base to a side opposite the substrate side. A face of the substrate opposing the rotor is provided with a FG pattern 19. When a distance between an end of the rotor frame on the substrate side and the substrate is taken as A, a distance between an end of the first extended portion on the substrate side and the substrate is taken as B, and a distance between the end of the first extended portion on the substrate side and the magnet is taken as G, B≦A≦B+G is satisfied. Accordingly, it is possible to improve the precision in detecting the rotational speed by reducing noise superimposed on the FG signal, while securing a high driving efficiency.