PURPOSE: To enable the diameter of a rotor to be made larger than the outer diameter of a motor, by forming an armature coil wound up in a solenoid shape with the diameter larger than that of the magnet rotor, and by fitting fixed pole groups independent in each phase, on the coil.

CONSTITUTION: On the outer peripheral side of a magnet rotor 2, a stator armature 1 provided with a plurality of fixed pole sections 11e∼11i independent in each phase is placed to form an inner rotor type brushless DC motor. First, the stator armature 1 is wound up with an armature coil 1b so that the diameter of the armature may be larger than that of the rotor 2 on the shaft same as that of the rotor 2. Then, through the both open end sides of the armature coil 1b, fixed poles 1a, 1c providing the outer peripheral side with magnetic combined units 11g, 11j and providing the inner peripheral side with the fixed pole sections 11e∼11i respectively are fitted. Accordingly, in case of setting a fan 2c in the rotor 2, or in a similar case, the diameter of the fan can be made larger than the outer diameter of the motor, and torque is also increased.