An LED backlight unit includes a light source; a board including a circuit pattern printed on an underside thereof, and having at least one mounting hole perforated therein where the light source is inserted; a metal chassis having an inside surface on which an underside of the light source is mounted, and receiving the board to be arranged in parallel to and with a gap from the metal chassis; and a reflector arranged on a top surface of the board to reflect light generated from the light source. The heat radiating path for transferring heat from the light source to the outside can be more simplified to enhance heat radiation efficiency thereby raising product reliability. The number of whole components can be reduced and the board with the light mounted thereon can be replaced with an inexpensive part thereby saving fabrication cost.