A gear includes a gear body to be attached to a distal end of a driving shaft in an axial direction of the driving shaft and including teeth each extending obliquely with respect to the axial direction, and a stopping portion included in the gear body and configured in such a manner as to allow the driving shaft to which the gear body is attached to move in a circumferential direction. When the driving shaft moves in the circumferential direction, the stopping portion is enabled to stop the gear body from moving in the axial direction, the stopping portion stopping the gear body by coming into contact with a portion of the driving shaft.