PROBLEM TO BE SOLVED: To facilitate further narrowing down of a frame while securing necessary strength of a planar lighting device.SOLUTION: Holding and positioning of components of a planar lighting device 10 is performed by a bottom part 16Ma, a first side wall 16Mb, and resin parts 16Ra, 16Rb which configure a frame 16. The bottom part 16Ma is made of a sheet metal, so that it becomes possible to secure strength necessary for the frame 16. Also, the resin parts 16Ra, 16Rb are arranged so as to oppose to an incident surface 12c of a light guide plate 12 and an end surface 12e opposing to the incident surface respectively, and when assembling the light guide plate 12 to the frame 16, positioning is performed by the resin parts 16Ra, 16Rb coming into contact with the light guide plate 12, so that occurrence of contamination can be suppressed. Then, at each of a side on the incident surface 12c side of the light guide plate 12 and a pair of sides for connecting end parts opposing to the light guide surface of
