To reduce an iron loss generated between an attraction plate and a ring-shaped magnet for driving a motor.

A brushless motor 10B is configured such that the ring-shaped magnet 26 for driving the motor, fixed onto the internal surface of a rotor yoke 24 on a rotor R side, is opposed to a stator core 16 on a stator S side with a slight air gap to obtain a rotary driving force, while the ring-shaped magnet 26 for driving the motor is opposed to the attraction plate 17 mounted on a stator base 11 on the stator S side with the slight air gap so as to control the movement of the axial direction of a rotor R. In such a brushless motor 10B, the ring-shaped magnet 26 for driving the motor is provided with a first surface 26c1 opposed to the stator core 16 and a second surface 26e opposed to the attraction plate 17 and a polar logarithm on the second surface 26e is set at a value smaller than that on the first surface 26c1.