PURPOSE: To obtain high-luminance light emission by chamfering an angular part between the surface of a light transmission plate and a side surface where a linear light source is arranged so that light made incident on the light transmission plate once may be reflected and guided to the inner part of the light transmission plate.

CONSTITUTION: In this surface light emitting device, the linear light source 2 is arranged on the side surface of the transparent light transmission plate 1 having outside dimension larger than a display area 9. A rectangular plate material is used as the light transmission plate 1, a chamfer part 7 is formed by chamfering the angular part between the surface of the plate 1 and the side surface where the light source 2 is arranged so that the light made incident on the plate 1 once may be reflected and guided to the inner part of the plate 1. The shape of the chamfer part 7 is a flat surface or a crosssection curved surface (projected surface or recessed surface), and the angle and dimension are properly set in accordance with the thickness of the plate 1, the size of the light source 2, a distance between the plate 1 and the light source 2 and other conditions. Acrylic, polycarbonate, polystyrene or acrylic styrene is used as the material of the plate 1.