A direct type backlight unit used in a liquid crystal display device is provided which can suppress lowering of luminance at an electrode portion of a linear light source. A reflecting plate is formed on a side wall of a box-shaped reflector close to an end of a linear light source. The reflector reflects light beams from the linear light source to be guided toward a liquid crystal panel. The reflecting plate on the side wall has at least two inclined surfaces. The inclined surfaces may have a stepped shape or a convex ridge shape. According to this arrangement, it is possible to reduce or eliminate decrease of the luminance level at ends of an effective display area of a liquid crystal panel.