To prevent generation of uneven brightness in the longitudinal direction of a light source by installing an illumination leading part between a rod- shaped light source and the incident surface of a plate-form member from which light is emitted, and leading the light from the effective region of the light source in such a way as spreading topward the end part.

Among the beams of illumination light emitted from a fluorescent lamp 11, the beam L2 emitted at the end of the effective light emission region AR is put incident from the oversurfaces of parallelogramic prisms 12b, 12c of an illumination light lead-in part 12 and is emitted in such a way as distributed to both ends of a light diffusive light-guide member 2. Accordingly a sufficient illumination light L2 is cast onto the end parts even in case the light guide member 2 is longer than the region AR of the lamp 11, and the brightness of the corresponding region is heightened. The illumination beam of light L3 emitted from a part near the central part is scattered within a trapezoidal prism 12a and put incident to the light guide member 2. In the light guide member 2, therefore, sufficient illumination light L3 is cast even onto the shade zones of the slopes of the prisms 12b, 12c, and it is possible to avoid uneven brightness in the emitted light.