To provide a backlight device for a display device capable of preventing unevenness in emitting light in a backlight device which reflects light from a light source on an end part of a U-shape in cross section of a reflecting sheet, introduces to an edge light incident part of a plate-shaped light guide body, and emits the light incident to the plate-shaped light guide body from a surface for emitting introduced light.

A space of a folding part of an end part 14 of a U-shape in cross section is larger than a thickness of a plate-shaped light guide body 3. A part overlapping an end part 11 of the end part 14 of a U-shape in cross section and an end part 12 of the plate-shaped light guide body 3 is attached with double-side adhesive tape 10, and a tubular light 7, a reflecting sheet 4, and the plate-shaped light guide body 3 are held in a case 1 having an opening surface 2. With this structure, even when the reflecting sheet for reflecting light from the light source and radiating to the plate-shaped light guide body is formed of resin, a position relation of the reflecting sheet 4 and the plate- shaped light guide body 3 does not change because of restoring force of the reflecting sheet 4, and unevenness of light emission does not occur.