PURPOSE: To achieve the miniaturization without causing a reduction in strength by forming the intermediate part of an output shaft having a pinion gear part formed on the shaft end to a large diameter, and helical spline bonding the inner circumferential part of the clutch inner cylinder of an over-running clutch to this intermediate part.

CONSTITUTION: In a DC electric motor 1, an intermediate bracket 50 having an internal gear 15 formed on the inner circumferential part is mounted to a yoke 2 having a field pole 3 formed of a permanent magnet in its inside, and a front bracket 51 is mounted to the intermediate bracket 50. A support ring 52 is rotatbly fitted to a rotating shaft 8, and the clutch outer cylinder 55 of an over-running clutch 54 connected to an epicyclic gear 14 is fixed to the support ring 52. A clutch inner cylinder 56 to be inserted into the outer cylinder 55 through a roller 23 for one-directional rotation is helical spline bonded (58a, 58b) to an output shaft 57 supported by the inner circumferential part of the rotating shaft 8 through a bearing 27 in such a manner as to be capable of relatively rotating and sliding, and a pinion gear part 59 is formed on the shaft end part of the output shaft 57.