Cold cathode tube 22 is covered with lamp reflector 31. An edge portion on the side of incident light surface 26a of light guide 26 is interposed between upper and lower edge portions 31a and 31b of lamp reflector 31. Reflection sheet 29 is attached to the back surface 26b of light guide 26. Reflection sheet 29 is fixed on the front surface of frame 32 by adhesive tapes 41 for electric insulation. An interposing width of "A" where the edge portion on the side of incident light surface 26a of light guide 26 is interposed between upper and lower edge portions 31a and 31b of lamp reflector 31, which is larger than a gap of "B" defined between step portion 35 of frame 32 and edge 26d of light guide 26. With the structure arranged above, the edge portion on the side of incident light surface 26a of light guide 26 is firmly held between upper and lower edge portions 31a and 31b of lamp reflector 31.