A backlight unit for slimmed structure and exhibiting uniform brightness through the improvement of its luminance efficiency and the quality in appearance of which is improved by the removal of bright lines, and a liquid crystal display device having the same are disclosed. The backlight unit includes a plurality of light emitting lamps disposed above a cover bottom such that the light emitting lamps are arranged at regular intervals, a diffusion plate disposed above the light emitting lamps, the diffusion plate including a substrate, a light control part formed on the bottom surface of the substrate corresponding to the light emitting lamps, and lens parts mounted on the top surface of the substrate, and an optical film disposed above the diffusion plate.