A backlight unit comprising: a frame including a bottom and a sidewall extending from the bottom, the frame including a first long side, a second long side opposite to and parallel to the first long side, a first short side adjacent to and positioned between the first long side and the second long side, and a second short side adjacent to and positioned between the first long side and the second long side, the second short side being opposite to and parallel to the first short side; at least one substrate located on the frame, and a plurality of light sources mounted on the at least one substrate; a reflecting sheet located on the at least one substrate, and a plurality of lenses, wherein 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; a second sheet part extending from the first sheet part in a first direction parallel to the first and second long side or parallel to the first and second short side, the second sheet part further extending in a second direction being parallel to the other one of the first and second long side and the first and second short side, and the second sheet part being inclined from the first sheet part on the bottom of the frame towards the sidewall of the frame, and a third sheet part extended from the second sheet part and located on the sidewall, the plurality of lenses are inserted into the plurality of holes and are coupled to the respective light source, wherein a portion of the light emitted through the plurality of lenses travels towards the second sheet part of the reflecting sheet, the second sheet part includes first areas and second areas alternately formed along the second sheet part in the second direction; the first areas are located to correspond to holes closest to the second sheet part, and the second areas are located between the first areas, at least the first areas have at least a first dot area and a second dot area, the first dot area and the second dot area are positioned at a respective different distance from the respective hole closest to the second sheet part in the first direction, a size of a dot in the first dot area is different from a size of a dot in the second dot area, and the dots in the first and second dot areas (P1, P2) reduce the reflectance of light of the reflecting sheet, characterized in that the first areas protrude to the plurality of holes further than the second areas. a frame including a bottom and a sidewall extending from the bottom, the frame including a first long side, a second long side opposite to and parallel to the first long side, a first short side adjacent to and positioned between the first long side and the second long side, and a second short side adjacent to and positioned between the first long side and the second long side, the second short side being opposite to and parallel to the first short side; at least one substrate located on the frame, and a plurality of light sources mounted on the at least one substrate; a reflecting sheet located on the at least one substrate, and a plurality of lenses, wherein 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; a second sheet part extending from the first sheet part in a first direction parallel to the first and second long side or parallel to the first and second short side, the second sheet part further extending in a second direction being parallel to the other one of the first and second long side and the first and second short side, and the second sheet part being inclined from the first sheet part on the bottom of the frame towards the sidewall of the frame, and a third sheet part extended from the second sheet part and located on the sidewall, 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 extending from the first sheet part in a first direction parallel to the first and second long side or parallel to the first and second short side, the second sheet part further extending in a second direction being parallel to the other one of the first and second long side and the first and second short side, and the second sheet part being inclined from the first sheet part on the bottom of the frame towards the sidewall of the frame, and a third sheet part extended from the second sheet part and located on the sidewall, the plurality of lenses are inserted into the plurality of holes and are coupled to the respective light source, wherein a portion of the light emitted through the plurality of lenses travels towards the second sheet part of the reflecting sheet, the second sheet part includes first areas and second areas alternately formed along the second sheet part in the second direction; the first areas are located to correspond to holes closest to the second sheet part, and the second areas are located between the first areas, at least the first areas have at least a first dot area and a second dot area, the first dot area and the second dot area are positioned at a respective different distance from the respective hole closest to the second sheet part in the first direction, a size of a dot in the first dot area is different from a size of a dot in the second dot area, and the dots in the first and second dot areas (P1, P2) reduce the reflectance of light of the reflecting sheet, characterized in that the first areas protrude to the plurality of holes further than the second areas.