A backlight unit comprising: a frame including a bottom area and a sidewall area extended from the bottom area; at least one substrate positioned at a front side of the frame, a plurality of light sources being mounted on the at least one substrate; a reflective sheet positioned at a front side of the at least one substrate and including a strip area in at least a portion of the reflective sheet, a reflectance of the at least the portion of the reflective sheet being different from a reflectance of at least another portion of the reflective sheet; and an optical sheet positioned at a front side of the reflective sheet, wherein the reflective sheet includes: a first sheet area contacting the bottom area of the frame and including a plurality of lens holes accommodating the plurality of light sources, and a second sheet area spaced apart from the bottom area of the frame wherein the strip area includes a plurality of strip areas, wherein the strip area is disposed in the second sheet area; and wherein the plurality of strip areas are disposed corresponding to the plurality of lens holes, wherein the strip area includes a first strip area disposed in parallel with a long side of the reflective sheet and a second strip area disposed in parallel with a short side of the reflective sheet and characterized in that the first strip area includes a plurality of lines formed in a direction parallel the long side of the reflective sheet and having a color different from a periphery of the plurality of lines and has a lower reflectance than the periphery of the plurality of lines, and wherein a color of each of the plurality of lines is increasingly darker, and so the reflectance of the lines decreases, when a distance increases from the corresponding of the plurality of light sources in a direction perpendicular to the long side of the reflective sheet. a frame including a bottom area and a sidewall area extended from the bottom area; at least one substrate positioned at a front side of the frame, a plurality of light sources being mounted on the at least one substrate; a reflective sheet positioned at a front side of the at least one substrate and including a strip area in at least a portion of the reflective sheet, a reflectance of the at least the portion of the reflective sheet being different from a reflectance of at least another portion of the reflective sheet; and an optical sheet positioned at a front side of the reflective sheet, wherein the reflective sheet includes: a first sheet area contacting the bottom area of the frame and including a plurality of lens holes accommodating the plurality of light sources, and a second sheet area spaced apart from the bottom area of the frame a first sheet area contacting the bottom area of the frame and including a plurality of lens holes accommodating the plurality of light sources, and a second sheet area spaced apart from the bottom area of the frame wherein the strip area includes a plurality of strip areas, wherein the strip area is disposed in the second sheet area; and wherein the plurality of strip areas are disposed corresponding to the plurality of lens holes, wherein the strip area includes a first strip area disposed in parallel with a long side of the reflective sheet and a second strip area disposed in parallel with a short side of the reflective sheet and characterized in that the first strip area includes a plurality of lines formed in a direction parallel the long side of the reflective sheet and having a color different from a periphery of the plurality of lines and has a lower reflectance than the periphery of the plurality of lines, and wherein a color of each of the plurality of lines is increasingly darker, and so the reflectance of the lines decreases, when a distance increases from the corresponding of the plurality of light sources in a direction perpendicular to the long side of the reflective sheet.