PURPOSE: To prevent displacement of a second operating knob to a second switch side when a first operating knob is operated by engaging with the engaging section of the second operating knob upon interlocking to a push of the first operating knob.

CONSTITUTION: When one of four first switches 18 is operated by pushing the edge of a first operating knob 19, a mirror 10 circularly moves to the left or right and upward or downward according to the respective directions of operation. Then, one end of a stopper lever 25 is pushed downward due to a tilt of the first operating knob, so that the other end of the stopper lever 25 is engaged with the locking section 22a of a second operating knob 22, which prevents the knob 22 from displacement to the second switch 21 side. When the first operating knob in a normal position, the second switch 21 is ON if the second operating knob 22 is pushed, and the mirror 10 is heated by a heater wire so that the cloudiness is removed. Even if the second operating knob 22 is operated by mistake when the first operating knob 19 is operated, displacement to the second switch 21 can be certainly prevented by the stopper lever 25.