A display device includes a display panel including a front substrate and a back substrate, a back cover positioned in the rear of the display panel, and a backlight unit positioned between the display panel and the back cover. The backlight unit includes a plurality of optical sheets. At least first optical sheet of the plurality of optical sheets includes an opening. At least second optical sheet of the other optical sheets except the first optical sheet among the plurality of optical sheets includes a protrusion corresponding to the opening of the first optical sheet.