<p>The present invention relates to a back light unit of a touch key installed at a rear surface of a touch panel on which characters and numbers are printed to supply light irradiated from a lateral light emitting diode to the touch panel. The back light unit of a touch key includes: a printed circuit board (100); a light emitting diode (200) mounted at a rear surface of the printed circuit board (100) to irradiate light; a case (300) having a′�′section structure and attached to a rear surface of the printed circuit board (100) to form a receiving space (44) and to receive the light emitting diode (200) inside the receiving space (44); a reflective film (400) adhering to an inner surface of the case (300) to reflect light irradiated from the light emitting diode (200); and a light guide film (500) attached to a front surface of the reflective film (400) to supply light irradiated from the light emitting diode (200) to the touch panel.</p>
