There is disclosed a backlight assembly for maximizing a light incidence efficiency by changing a construction of a light guide plate and a liquid crystal display device having the same. A light incidence surface of the light guide plate receiving a light from a lamp is inclined to make an obtuse angle with a light-emitting surface through which the light is transferred to the display unit. An open surface of a lamp cover that is disposed to face towards the light incidence surface is formed to have the same inclined angle as the light incidence surface of the light guide plate. In addition, a light reflecting plate and an optical sheet are respectively disposed on the top and bottom surfaces of the light guide plate, on which light absorbing layers, for absorbing light that leaks from the light guide plate, are formed at both ends thereof. Accordingly, there are advantages in that the light incidence efficiency of the light is improved even though a thickness of the light guide plate is not increased, and that it is possible to remove the light concentrated at an edge of the light incidence surface of the light guide plate.