A light guide plate of a backlight unit is provided to remove a bright line around a light entrance surface by further forming a prism pattern in a direction in parallel to the light entrance surface on a bottom surface of the light guide plate that employs a prism pattern perpendicular to the light entrance surface. A light guide plate(10) includes one side surface serving as a light entrance surface(11a) and an upper surface serving as a light emitting surface(12). A first prism pattern(13) is formed on a bottom surface of the light guide plate from the light entrance surface to an opposite light entrance surface(11b) in order to uniformly emit a light entering from the light entrance surface to the upper surface of the light guide plate at a constant angle. A second prism pattern(14) is formed on the bottom surface of the light guide plate at the light entrance surface in order to disperse a light from the light entrance surface. The second prism pattern has a shape of an asymmetric wedge that is in parallel to the light entrance surface and has slant surfaces of different lengths.
