To prevent damage of commutator segments or junction of a commutator segment and a metal segment in the case of fusing in a disk type commutator of outer surface junction structure, while restraining manufacturing process from complicating.

A metal segment 2 bonded to the outer surface of the commutator segment 1 has a commutator segment connection part 21 bonded to the commutator segment 1 and a boss part combining part 22 fixed to the boss part 3. The boss part combining part 22 has a boss part fixing part 220 on the terminal side, and an easily deforming part 222 on the commutator segment connection part 21 side. The deforming part 222 deforms easily by thermal expansion of the metal segment 2 in the case of fusing. As a result, it does not happen that the junction of the commutator segment connection part 21 of the metal segment 2 and the commutator segment 1 is peeled by thermal expansion of the metal segment 2 in the case of fusing.