To widen a rear view field from the driver's seat side in a vehicle, allow reverse while confirming a rear wheel in the reverse, simplify structure, and reduce a manufacturing cost.

A mirror guide 4 for guiding an auxiliary mirror 3 freely movably is provided in a door mirror box 1 so as to project out the plane auxiliary mirror 3 stored inside the door mirror box 1, a moving plate 5 is bonded onto a reverse face of the auxiliary mirror 3, an energized spring 6 for projection is attached thereto to project out the plate 5, a locking means 7 for holding the moving plate 5 lockingly is provided in an upper part of the plate 5, and a releasing button 8 for releasing the locked condition by the locking means 7 is provided to project its tip from the door mirror box 1.