To provide both light-transmissivity and retroreflectivity and to improve strength and weatherproofness by placing a light-transmissive retroreflective sheet on the front surface of a light-transmissive display board and interposing a light-transmissive reinforcing member between the display board and the light-transmissive supporting board which is placed at a specified distance behind the display board.

The front surface of a light-transmissive display board 1 formed from a homogeneous plate of acrylic resin or the like is provided with a light- transmissive, retroreflective, and e.g. prismatic sheet 2 whose surface is installed with a display section such as traffic sign. And on the back side of the display board 1, a light-transmissive supporting board 3 composed from a semi-transparent white diffusion plate at a specified distance from the display board 1 roughly parallelly to the board 1 and further a light-transmissive reinforcing element 4(frame-like member) between the display board 1 and the supporting board 3 are provided. And the space formed by two reinforcing elements, the display board 1 and the supporting board 3 has opening sections 5 at its two ends in the vertical direction, and sections communicating between the openings 5 are provided.