A surface luminous lighting unit has a light panel comprising a plurality of light guiding plates laminated in different lengths. The longer side of the light panel is made shorter than the distance between filaments of a lamp, and longer than the distance between the portions where a luminance of the lamp is equal to 75% of the maximum luminance of the lamp. The surface luminous lighting unit comprises a light guide which comprises a plurality of light guiding plates in different length laminated in such a manner that the sides of those plates where light enters are made level with each other, where the other sides thereof are arranged in a step-like. A linear light source is affixed to the light entering side of the light guide, and a reflector is affixed to the light exiting side of the light guide in such a manner as to extend thereover.
