A backlight unit capable of reducing or effectively preventing a luminance deviation includes a plurality of light emitting diodes, a light source substrate on which the plurality of light emitting diodes is mounted, a light guide plate converting line-shaped light generated from the light emitting diodes into a surface-shaped light, an incident surface of the light guide plate contacting an emitting surface of each of the light emitting diodes, a first fixing part formed on the light source substrate in a region overlapping the light guide plate and a second fixing part formed on the light guide plate and coupled to the first fixing part.