A liquid crystal display device includes a liquid crystal panel; a main frame surrounding sides of the liquid crystal panel; a backlight unit disposed under the liquid crystal panel and surrounded by the main frame, the backlight unit including a light guide plate, a lamp at a side of the light guide plate, a reflector under the light guide plate and an optical sheet on the light guide plate, wherein a rear surface of the reflector is exposed through an opening of the main frame; and a protection sheet attached to the rear surface of the reflector to protect the rear surface of the reflector and including a protruding part at a side of the protection sheet, the protection sheet has a rectangular shape.