Disclosed herein is a backlight unit, capable of easily forming a curved or three-dimensional shape. The backlight unit according to the present invention comprises a light guide panel which includes a light guide plate having on one surface or both surfaces thereof a plurality of notches, an uneven dot pattern, a printed dot pattern or a sanded surface, or a light diffusion plate; a luminous means which includes a lamp mounted on a PCB to emit light to the light guide panel; a groove formed along an edge of the light guide panel so that the luminous means is installed in the light guide panel; and a thin heat radiating plate fixed on a back surface of the PCB along the groove.