A backlight unit includes light emitting diodes (LED's) and light guide plate which guides light from the light emitting diodes to liquid crystal panel and is constructed so that light is emitted from light emission plane of light guide plate opposite to liquid crystal panel toward liquid crystal panel. Area of light emission plane of light guide plate is smaller than effective display area of liquid crystal panel and predetermined shape for diffusing or dispersing light is formed on a lateral side perpendicular to light emission plane of light guide plate and/or at an edge portion near the lateral side of the light emission plane.