There is provided an actuator including a motor and a case adapted to house the motor. In the actuator, an output shaft of the motor is supported by a structured configured such that an elastic member is disposed between the case and at least one end of the output shaft, wherein the elastic member is in contact with a portion of the case in an engaging manner whereby the elastic member is prevented from shifting relative to the case in the rotation direction of the output shaft, and also wherein the elastic member is in contact with a portion of the motor in an engaging manner whereby a body of the motor is prevented from shifting relative to the elastic member in the rotation direction of the output shaft.