To attain expansion of the effective area of a light guide by providing to a surface a brim part protruded toward a light source direction so as to match an emission surface.

A brim part 3 protruded toward a light source 2 direction is provided to an emission surface 1a of an incident surface 1c so as to match the emission surface 1a, a light guide 1 to which frost processing 3a is applied is formed on the surface of the light source 2 side of the brim part 3. By providing the brim part 3 to which frost processing 3a is applied on the surface of the light source 2 side, the light of that part is scattered, the light quantity directly leaked from the emission surface 1a is reduced, and the generation of light non-uniformity is reduced.