In a backlighting device for use with display panels that comprises a light conducting plate made of a light-transmissive material, one of the major faces of said light conducting plate being provided with a light diffusing capability and covered with a specular or light diffusing/reflecting plate, and a linear light source provided in proximity to the end portion of at least one side of said light conducting plate, the improvement wherein at least one sheet that is made of a light-transmissive material and that has a multiple of raised structures having straight ridgelines at minute intervals on the same side in such a manner that the ridgelines are substantially parallel to one another or at least one sheet that is made of a light-transmissive material and that has a multiple of pyramidal or conical projecting structures at minute intervals on the same side, said projecting structures having portions of such a shape that the vertical angles are substantially the same, is provided on the exit face of the light conducting plate in such a way that either type of structures face outward.