A backlight unit assembly using a light emitting diode array in a liquid crystal display device is disclosed in the present invention. The backlight unit assembly includes a light emitting diode array having a plurality of red, green, and blue light emitting diodes emitting respective light, a first housing concentrating the light emitted from the light emitting diode array to a first direction, a sub-light guiding plate positioned at one side of the light emitting diode array mixing the light to form white light, a main-light guiding plate guiding the light incident on the sub-light guiding plate to a second direction, and a pair of holders at the left and right side portions of the light emitting diode array preventing the light from leaking to the outside of the backlight unit assembly.