To make a triangular display in an instant without assembly operation.

A recessed shape is provided at a part of each of a glass 1 and a glass 2, and a red bulb 3 is provided in a space part formed by joining the glass 1 and glass 2. Stabilizing liquid 5 is put to prevent the damage of the red bulb 3 provided in the space part of the joined glass 1 and glass 2. A bulb triangular display automobile rear window device is thereby installed at a rear window of an automobile, and a bulb triangular display is made only by switch operation.