A rotor is accommodated in a yoke housing. Six magnets are arranged at equal intervals in the circumferential direction on the inner circumferential surface of the yoke housing so as to face the rotor. The core is generally cylindrical and includes an annular portion at an anti-output side and a balance at an output side. The magnets have six poles so as to effectively narrow a basal path width of the core in which the line of magnetic force concentrates most and magnetic saturation is likely to occur most. This reduces the diameter of the core. Therefore, the motor is effectively miniaturized in the axial direction and in the radial direction without complicating the formation steps.