A backlight unit including a frame including a bottom and a sidewall extending from the bottom; at least one substrate located on the frame, and a plurality of light sources mounted on the at least one substrate; and a reflecting sheet located on the at least one substrate. The reflecting sheet comprises a first sheet part located on the bottom, the first sheet part including a plurality of holes corresponding to the plurality of the light sources; and a second sheet part extended from the first sheet part, the second sheet part including a horizontal dot area located along a long side of the reflecting sheet and a vertical dot area located along a short side of the reflecting sheet, and at least one of the horizontal dot area and the vertical dot area comprising first areas and second areas. In addition, the first areas correspond to outermost holes among the plurality of holes, and the second areas are located between the first areas, the first areas and the second areas include a plurality of dot areas, each of the dot areas includes a plurality of dots, a density of dots included in one of the plurality of dot areas is different from a density of dots included in another of the plurality of dot areas in the first area, a density of dots included in one of the plurality of dot areas is different from a density of dots included in another of the plurality of dot areas in the second area, the first and second areas comprise first dot areas, the first dot areas are positioned at the same distance between a first distance and a second distance from a line, the line being an imaginary line connecting the outermost holes along at least one of the long side and the short side of the reflecting sheet, and a density of dots included in the first dot area of the first area is different from a density of dots included in the first dot area of the second area.