PURPOSE: To reduce the initial breakdown at the time of a commutator fixing work in the manufacturing process of a motor, provide the satisfactory molding workability of commutators and improve the coaxial accuracy between the commutators and a shaft.

CONSTITUTION: The rotor of a motor has a shaft 4 which is supported inside a stator 5 having field poles 5a by bearings (not shown) so as to be able to rotate, a magnetic core 6 fixed to the middle part of the shaft 4, a plurality of coils 7 which are provided near the outer circumference of the magnetic core 6 and connected electrically to the slots of conductor parts 1 by a method such as heat welding and commutators 3 which are pushed into and fixed to the shaft 4. The commutators 3 are molded with resin 2 into one piece with a plurality of the conductor parts 1 which are arranged along the outer circumference cylindrically. The inner circumference of the resin molding 2 of the commutators 3 is tapered and its middle part 2a has a minimum diameter b and, the closer to the end part, the larger the diameter.