To facilitate illuminations for showcases such as an upward illumination, a downward illumination and a simultaneous illumination of the up and downward illuminations including the store and price tags indicating light.

The device regards one plane of transparent board having a light permeability as a transparent plane, a cold-cathode tube 16 which receives light incident from one end plane of the light conductor plate 17 having a reflection means 18 on the other plane facing against the transparent plane, is placed on the showcase 13. In the case of illuminating a plural number of the stages of showcases 14 and 15, a reflection means 23 which does not counter- act with the reflection means 22 of the reverse plane is installed on the surface of the inclined part 21a provided on the light conductive plate 21 that radiates light toward the lower showcase 15 from the cold cathode tube placed on the upper showcase 14. A back light illumination can be made by placing a light- permeable price tag medium 19 and a light-permeable front shop display medium on the front planes of inclined parts 17a and 21a.