Disclosed herein is a backlight unit equipped with LEDs. The backlight includes an insulating substrate, a plurality of LED packages, an upper heat dissipation plate, and a lower heat dissipation plate. The insulating substrate is provided with predetermined circuit patterns. The LED packages are mounted above the insulating substrate, and are electrically connected to the circuit patterns. The upper heat dissipation plate is formed on the insulating substrate, and is configured to come into contact with the circuit patterns and to dissipate heat. The lower heat dissipation plate is formed on the insulating substrate, and is configured to transmit heat transmitted through the upper heat dissipation plate. The upper heat dissipation plate and the lower heat dissipation plate are connected to each other by at least one through hole, and the through hole and the upper heat dissipation plate have a predetermined area ratio.