The invention is intended to provide a lighting device that shortens time required to obtain peak brightness. A backlight unit 16 according to the invention includes: cold cathode tubes 22 as a light source; a chassis 18 housing the cold cathode tubes 22; a reflection sheet 21 disposed within the chassis 18 and reflecting light; and a heat insulator 27 disposed between the chassis 18 and the reflection sheet 21. Because the heat insulator 27 is disposes between the chassis 18 and the reflection sheet 21, heat in the chassis 18 is less likely to escape to the outside. Therefore, the temperature inside the chassis 18 can be efficiently increased with the heat generated by the cold cathode tubes 22.