The present disclosure relates to a back light unit having an LED array structure for reducing light leakage problem at edge portion. A liquid crystal display device comprises a liquid crystal display panel; an optical sheet disposed under the liquid crystal display panel; and an LED array having red LED, green LED and blue LED are sequentially arrayed under the optical sheet, wherein one portion of an outermost LED of the LED array is included within an area covered by the liquid crystal display panel, and other portion of the outermost LED of the LED array is excluded from the area covered by the liquid crystal display panel.