A backlight unit is discussed, which includes 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, wherein the reflecting sheet includes: 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; a second sheet part extended from the first sheet part, the second sheet part including first areas and second areas; and a third sheet part extended from the second sheet part and located on the sidewall.