PURPOSE: To provide a triangular display board unit for an automobile capable of demonstrating the excellent display and discriminating performance effectively using a rear spoiler.

CONSTITUTION: A triangular display board unit is provided with a lamp body 3 mounted on a rear spoiler 2 so as to be capable of irradiation at least to the rear and upper parts, a frame board which is arranged to be attached to the upper side of the lamp body 3, foldable at the center part, and slidably supports both end parts on each side of the lamp body 3, guide rails which are arranged on both sides of the lamp body 3, and slidably support the respective end parts of the frame board 4 in the width direction of the rear spoiler 2, and a pair of reflecting members 8 which are openably/closably supported on the rear surface of the frame board 4. The respective end parts of the frame board 4 are slid to be brought close to each other to be inclined on the lamp body 3, and the reflecting members 8 are expanded from the frame board 4 by the specific angle.