A backlight unit includes a light source array including at least one light source which emits light and a circuit board on which the light source is disposed, and a first optical layer disposed on the light source array. The first optical layer includes a first layer which defines at least one concave portion in a bottom of the first layer, where the at least one concave portion is coupled to the light source, a second layer disposed on the first layer, the second layer guiding light incident from the first layer in one direction, a plurality of optical patterns disposed on one surface of the second layer, the plurality of optical patterns selectively emitting light passing through the one surface, and a reflective layer disposed on the bottom of the first layer.