To source a spacing between a fluorescent tube and a lamp reflector, to improve the luminance of a lighting surface, to improve luminance unevenness and to obtain the excellent characteristic of the uniformity of the luminance of the lighting surface by attaching a spacer member to the outer periphery of the fluorescent tube.

The fluorescent tube 1 being a light source is arranged at least at one end of the side surface of a transparent light guide body 3 and surrounded by the lamp reflector 2a whose inner surface is covered by a high reflection layer. Then, at least one spacer member 6a is attached to the tube 1 between the tube 1 and the reflector 2a. Thus, the uniformity of the spacing between the tube 1 and the reflector 2a is secured and the direction of reflected light from the reflector 2a is made regular. By securing the distance between the tube 1 and the reflector 2a, the distance between the tube 1 and the light guide body 3 is secured simultaneously. Therefore, a surface light source excellent in the uniformity of the luminance of the lighting surface is obtained because the light made incident on the light guide body 3 is made uniform.