The invention provides a small-sized motor. The motor comprises a housing for containing a permanent magnet stator and a rotor. The rotor is composed of a rotor iron core and a cylindrical commutator. The diameter of the rotor iron core is 20 mm. The diameter of the cylindrical commutator is smaller than 18 mm. The output power of the motor is larger than 36 watts. The expected service life of the motor is at least 750 hours.