A liquid crystal display device capable of preventing a split between a light guide plate and a prism sheet disposed at an upper side thereof and improving concentration efficiency, the device including a liquid crystal panel configured to represent an image, a lamp disposed below the liquid crystal panel to provide light to the liquid crystal panel, a light guide plate having the lamp disposed at least at one side thereof, and a birefringence optical sheet disposed between the liquid crystal panel and the light guide plate, and having a first prism pattern with a first refractive index, the pattern facing the liquid crystal panel, and a second prism pattern with a second refractive index higher than the first refractive index, the pattern facing the light guide plate.