A backlight unit includes a light guide plate including a first incident surface; a light source module including a first sub-light source module overlapping the first incident surface of the light guide plate in a first direction, where the first sub-light source module provides light to the first incident surface; and a distance adjusting member including a first sub-distance adjusting member overlapping the first incident surface of the light guide plate in the first direction and disposed at a first side of the first sub-light source module and a second sub-distance adjusting member disposed at a second side of the first sub-light source module, which is opposite to the first side of the first sub-light source module. The first sub-distance adjusting member and the second sub-distance adjusting member may move the light guide plate in the first direction.