An input disk, a clutch disk and wave washers are installed to an output shaft to form an output shaft assembly of a motor apparatus. The input disk is axially non-detachable from the output shaft and is rotatable about an axis of the output shaft. The input disk is driven by a drive force supplied from a motor main body of the motor apparatus. The clutch disk is supported by the output shaft in such a manner that the clutch disk is non-rotatable relative to the output shaft and is axially movable along the output shaft relative to the input disk. The wave washers apply a resistive force against axial movement of the clutch disk from a coupled state, at which the input disk is coupled with the clutch disk to rotate together.