A backlight unit for a display device includes a light guide plate; a reflective sheet under the light guide plate; a lamp at least one side of the light guide plate and providing a light into the light guide plate; and an optical sheet disposed on the light guide plate and including a first lenticular sheet, the first lenticular sheet including a base film for diffusing the light through the light guide plate, a first lenticular lens disposed on a front surface of the base film and having a half-cylinder shape and a first printing pattern on at least one edge of a rear surface of the base film.