A light guide plate includes at least one incident surface into which light is incident, an exit surface at least one end of which is connected the incident surface and through which the light is output, an opposite surface spaced apart from the exit surface and opposing the exit surface, and a plurality of reflective patterns extending from the exit surface toward the opposite surface. When a direction from the exit surface to the opposite surface is referred to as a first direction, a direction perpendicular to the incident surface is referred to as a second direction, and a direction parallel to the incident surface and perpendicular to the first direction is referred to as a third direction, a length of each reflective pattern in the first direction is smaller than a distance between the exit surface and the opposite surface, and a length of each reflective pattern in the second direction is larger than a length of each reflective pattern in the third direction.