According to one embodiment, a backlight device includes a support frame including a first frame body including a pair of first frame members and a second frame member connected to respective ends of the first frame members and a second frame body being separate from the first frame body, which connects other respective ends of the first frame members to each other, a reflective sheet on the support frame, a light guide on the reflective sheet within the support frame, an optical sheet on the light guide, and a light source unit in the support frame. The light source unit includes a wiring board on the second frame body and a light source on the wiring board, opposing an incidence surface of the light guide.