A gear mechanism may include a first gear, a second gear engaged with the first gear, and a stopper part formed in the second gear. The stopper part may be engaged with the first gear to prevent turning of the first gear. The stopper part is a part where a tooth is not formed in an outer peripheral part of the second gear. The stopper part includes a protruded part protruded to an outer side in a radial direction with respect to a tooth tip circle of a tooth part of the second gear, and a recessed part recessed to an inner side in the radial direction with respect to the protruded part and adjacent to the protruded part in a circumferential direction and, when turning of the first gear is stopped, a tip end side of the tooth part of the first gear is abutted with the recessed part.