A clutch includes a clutch inner and a clutch outer that houses the clutch inner and that transmits or interrupts torque between itself and the clutch inner. The clutch outer has a thick portion that has a larger thickness than the other portions of the clutch outer. A position-of-center-of-gravity adjusting portion for bringing the center of gravity of the clutch close to the axial center of a driven shaft is formed at a position separate from the axial center of the driven shaft of the thick portion. Efficiency of manufacture work of bringing the position of the center of gravity close to the center of rotation is thereby enhanced.