A backlight unit is disposed at a lower side of a liquid-crystal display module LCD, and has a case that accommodates a fluorescent tube, as a light source for light incident to the liquid-crystal display module, a lamp reflector that accommodates the fluorescent tube, and an optical waveguide having an approximately square shape in the surface that converts linear light generated by the fluorescent tube and light of the linear light reflected from the lamp reflector into planar light, and inputs the planar light to the liquid-crystal display module. The lamp reflector is made of metal, and has stoppers provided at first parts facing both ends of a side surface of the optical waveguide opposite to the fluorescent tube, at positions closer to the optical waveguide than to a second part facing the side surface of the optical waveguide excluding the first parts. With this arrangement, it is possible to provide a backlight unit of a liquid-crystal display device that can prevent the fluorescent tube from being damaged even when the optical waveguide drops due to shock or the like.