A backlighting device for display panels operating on the edge lighting method that comprises a light conducting plate made of a light-transmissive material, a layer of light-diffusing material that partly covers one major surface of the light conducting plate, and a light diffusing/reflecting plate that covers the thus covered area of the light conducting plate. The light conducting plate is provided on its exit face with a film that is coarser grained on the exit face than on the entrance face (the side closer to the light conducting plate) and which, when provided on the exit face of the light conducting plate, will increase the luminance of light issuing from the exit face of the light conducting plate. This backlighting device produces satisfactory luminance and can be used as a high-performance model that achieves a high efficiency of power to luminance conversion at least in the direction of the line normal to the exit face.