A backlight unit and a display device including the backlight unit are disclosed. The backlight unit includes a frame including a bottom area and a side area extended from the bottom area, at least one substrate positioned at a front surface of the frame and mounting a plurality of light sources, a reflective sheet positioned at a front surface of the at least one substrate and including a strip area in at least a portion of the reflective sheet, and an optical sheet positioned at a front surface of the reflective sheet. A reflectance of the at least the portion of the reflective sheet is different from a reflectance of at least another portion of the reflective sheet.