The present invention relates to a backlight unit with sag control patterns, comprising a light source formed in a side surface of a light guide plate; and a plurality of optical patterns formed on a lower surface of the light guide plate, sag of the plurality of optical patterns increasing as the optical patterns become more distant from the light source. By controlling sag of optical patterns formed in a light guide plate, efficiency of light emitted from a backlight unit can be improved and uniformity of the light can be maintained. Also, since sag of optical patterns can be controlled, by increasing the number of optical patterns (by improving fill factor), light efficiency and uniformity can be controlled easily. Also, compared with a conventional method for manufacturing white dot patterns, white dot patterns can be more efficiently manufactured in terms of development time and costs.