In a light guide plate and a backlight unit, a light guide plate includes a light incident surface, an opposite surface, a top surface, a bottom surface, and a plurality of optical path changing units. The optical path changing units are aligned on at least the bottom surface of the top surface and the bottom surface at a predetermined interval while protruding in parallel to a reference line perpendicular to the light incident surface. Accordingly, power consumption used to generate the light may be reduced.