A backlight unit of an embodiment includes: a light emitting module including a plurality of light emitting diodes and a module substrate on which the light emitting diodes are mounted; a bottom cover accommodating the light emitting module; a board on the bottom cover; a transformer mounted on a lower portion of the board, and including a core and a coil surrounding at least one portion of the core; a transformer cover covering the transformer; and a heat dissipating cover between the transformer cover and the bottom cover.