A backlight unit comprising: a frame of rectangular shape in plan view including a rectangular bottom and a sidewall extending from the sides of the bottom; a substrate located on the bottom of the frame, and a plurality of light sources mounted on the substrate; and a reflecting sheet of rectangular shape in plan view located on the substrate, wherein the reflecting sheet comprises: a rectangular 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 sides of the rectangular first sheet part; and a third sheet part extending from the second sheet part and located on the sidewall, wherein the light sources are arranged to direct at least a portion of the emitted light towards the second sheet part, and wherein the second sheet part is inclined from the first sheet part towards the third sheet part and comprises horizontal dot areas formed on the long sides of the reflecting sheet and vertical dot areas formed on the short sides of the reflecting sheet each having dots reducing the reflectance of light, said horizontal and vertical dot areas (HDA, VDA) each containing a plurality of dot areas (HDA1, HDA2, HDA3, VDA1, VDA2, VDA3) positioned sequentially in a direction from the first sheet part to the third sheet part and the plurality of dot areas (HDA, VDA) include a first dot area (HDA1, VDA1) and a second dot area (HDA2, VDA2), the first dot area (HDA1, VDA1) including a plurality of dots having the same size and the second dot area (HDA2, VDA2) including a plurality of dots having the same size, wherein the size of the plurality of dots in the first dot area (HDA1, VDA1) is different from the size of the plurality of dots in the second dot area (HDA2, VDA2), and characterized in that, in a corner of the reflecting sheet, the horizontal dot area and the vertical dot area are separated in plan view by different angles (DA1, DA2) from an imaginary line connecting said corner to the center point of the hole closest to said corner. a frame of rectangular shape in plan view including a rectangular bottom and a sidewall extending from the sides of the bottom; a substrate located on the bottom of the frame, and a plurality of light sources mounted on the substrate; and a reflecting sheet of rectangular shape in plan view located on the substrate, wherein the reflecting sheet comprises: a rectangular 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 sides of the rectangular first sheet part; and a rectangular 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 sides of the rectangular first sheet part; and a third sheet part extending from the second sheet part and located on the sidewall, wherein the light sources are arranged to direct at least a portion of the emitted light towards the second sheet part, and wherein the second sheet part is inclined from the first sheet part towards the third sheet part and comprises horizontal dot areas formed on the long sides of the reflecting sheet and vertical dot areas formed on the short sides of the reflecting sheet each having dots reducing the reflectance of light, said horizontal and vertical dot areas (HDA, VDA) each containing a plurality of dot areas (HDA1, HDA2, HDA3, VDA1, VDA2, VDA3) positioned sequentially in a direction from the first sheet part to the third sheet part and the plurality of dot areas (HDA, VDA) include a first dot area (HDA1, VDA1) and a second dot area (HDA2, VDA2), the first dot area (HDA1, VDA1) including a plurality of dots having the same size and the second dot area (HDA2, VDA2) including a plurality of dots having the same size, wherein the size of the plurality of dots in the first dot area (HDA1, VDA1) is different from the size of the plurality of dots in the second dot area (HDA2, VDA2), and characterized in that, in a corner of the reflecting sheet, the horizontal dot area and the vertical dot area are separated in plan view by different angles (DA1, DA2) from an imaginary line connecting said corner to the center point of the hole closest to said corner.