According to one embodiment, a backlight device includes a frame formed of a sheet material, a first adhesive layer provided on one surface of the frame, a reflective sheet attached to the frame with the first adhesive layer, an optical member disposed on the reflective sheet in the frame, and a light source disposed in the frame and configured to emit light to the optical member. In at least a part of the frame, a width of the frame and a width of the first adhesive layer are equal to each other, and at least an external surface of the frame and an external surface of the first adhesive layer are flush with each other.