PURPOSE: To offset cogging torque and to control the decrease amount of effective magnetic flux by equalizing the number of poles to divisors of the number of slots, classifying the area of poles of a magnetization of a permanent magnet into two kinds and, at the same time, making difference between wider area and narrower area of the poles of the magnetization as a portion of one slot pitch.

CONSTITUTION: The number of poles of a brushless motor are four poles, slots 13 of a stator core 12 are twenty-four pieces and are arranged at equal angles, and the number of poles are divisors of the number of slots. Area θ11, θ12, θ13 and θ14 of poles of a magnetization are classified into two kinds of 97.5, 97.5, 82.5 and 82.5, and they are so constituted that difference between wider area and narrower area makes a portion of one slot pitch. Value of cogging torque becomes zero, and an amount of effective magnetic flux is not so greatly decreased. Accordingly, the efficient brush-less motor having less vibration and noise during the operation and having higher output is obtained.