A retracting mechanism, which rotates a mirror for viewing a region substantially to a rear of the vehicle, has a motor, a cover which accommodates another end side of the motor, and a case main body which accommodates one end side of the motor and is rotatably supported at a vehicle body. In the retracting mechanism, the case main body and the cover are positioned due to a first fit-together portion, which is provided at a hanging-down wall of the cover, and a second fit-together portion, which is provided at a standing wall of the case main body, fitting-together with one another. The first fit-together portion and the second fit-together portion are both formed in shapes which are concentric with a rotating shaft. Accordingly, accuracy of positioning the case main body and the cover can be ensured to be good with the rotating shaft as a reference.