A liquid crystal display device having brightness uniformity at its front and lateral sides is provided according to one or more embodiments. In one embodiment, the liquid crystal display device includes a reflection sheet reflecting light, an optical plate including a substrate for guiding light, a height-varying portion formed on one surface of the substrate, not facing the reflection sheet, and a prism pattern formed on the height-varying portion, and a plurality of light sources arranged on one lateral surface of the optical plate in a first direction so as to correspond to a position of the height-varying portion having a height not greater than an average height from the one surface of the substrate to the height-varying portion, wherein the prism pattern extends in a second direction substantially perpendicular to the first direction, and the average height is in a range of about 0.1% to about 10% of the thickness of the substrate.