A light guide plate having a light-emitting surface with reduced luminance unevenness and a backlight unit using the light guide plate are provided. The light guide plate has a light entrance surface with two opposite lateral edges and a pair of widthwise edges extending between the lateral edges. Two opposite side surfaces extend from the lateral edges of the light entrance surface substantially at right angles to the light entrance surface. A light exit surface extends from one of the widthwise edges substantially at right angles to the light entrance surface. The light guide plate further has a surface opposite to the light exit surface that extends from the other of the widthwise edges. The side surfaces have respective light-scattering regions near the light entrance surface to scatter and reflect light entering the light guide plate through the light entrance surface and reaching the light-scattering regions.