To provide a process for manufacturing an assembly type commutator in which a plurality of commutator segments are secured firmly to the outer circumferential surface of an insulating substrate through a simple arrangement without using any insulating ring, and the commutator segments are secured surely regardless of dimensional variation.

A plurality of commutator segments 20 each having an arcuate commutator portion 21 and a riser portion 22 continuous to the commutator portion 21 are secured to the outer circumferential surface of a tubular insulating substrate 10 while providing a slit 23 between respective commutator segments 20. A plurality of grooves 15 are formed at predetermined positions of a flange portion 12 provided on the proximal end side of the insulating substrate 10, and each groove 15 is fitted with the riser portion 22. Under the state where the groove 15 is fitted with the riser portion 22, opening side is deformed plastically and a portion 15a swelling in the direction of the riser portion 22 is formed. The swelling portion 15a presses the proximal portion of the riser portion 22 and the riser portion is bonded into the groove 15.