A liquid crystal display device includes a liquid crystal display panel. A light guide plate is disposed at a rear side of the liquid display panel. The light guide plate has an exiting surface facing the liquid crystal panel and a reflecting surface opposite to the exiting surface. The reflecting surface has a plurality of grooves. A light source unit is disposed along at least one side of the light guide plate. The reflecting surface includes a first region formed the groove of a first length and a second region formed with groove of a second length shorter than the first length.