A clutch mechanism of the present power device comprises a fixed gear member, a moving gear member engaged with the fixed gear member when moving to a clutch connecting position, an armature for moving the moving gear member to the clutch connecting position when rotated relatively to the moving gear member, an electromagnetic coil unit for applying a brake resistance to the armature, and a clutch holding surface for abutting against the moving gear member when the electromagnetic coil unit is turned off in the clutch connecting state and for holding the moving gear member at a brake-clutch connecting position. The abutment of the moving gear member against the clutch holding surface is released by rotating the moving gear member relatively to the armature in a state in which the electromagnetic coil unit is operated.