A liquid crystal display device having includes a light guide plate having a surface thereof serving as an illuminating surface region opposite to a liquid crystal display panel, light sources mounted on a flexible printed-circuit board and provided on a side face of the light guide plate, an optical sheet member interposed between the liquid crystal display panel and the light guide plate. The side surfaces of the light guide plate with the light sources provided thereon have a ridge-like inclined surface formed thereon, when viewed from the illuminating surface, and the ridge-like inclined surfaces serve as a light-receiving surface with the light source arranged thereon.