A backlight unit comprising: a bottom cover having an inside surface and an outer surface opposing the inside surface, the bottom cover comprising a lower portion; a light emitting module arranged in the bottom cover, the light emitting module comprising: a module substrate; and a light emitting element formed on a first major surface of the module substrate; a first heat sink arranged on the outer surface of the bottom cover; and a second heat sink being in contact with the first heat sink and the light emitting module, the second heat sink comprising: a first heat radiating part contacting a side surface of the module substrate and the upper surface of the first heat sink, and a second heat radiating part bent from the first heat radiating part and contacting the second major surface of the module substrate, and arranged to the inside surface of the bottom cover, characterized in that the bottom cover further comprises a side portion; the light emitting module is arranged on the side portion of the bottom cover; a recess is provided in the lower portion of the bottom cover; the first heat radiating part of the second heat sink is inserted in the recess; and the upper surface of the first heat sink contacts the lower surfaces of both the first heat radiating part of the second heat sink and the bottom cover. a bottom cover having an inside surface and an outer surface opposing the inside surface, the bottom cover comprising a lower portion; a light emitting module arranged in the bottom cover, the light emitting module comprising: a module substrate; and a light emitting element formed on a first major surface of the module substrate; a first heat sink arranged on the outer surface of the bottom cover; and a second heat sink being in contact with the first heat sink and the light emitting module, the second heat sink comprising: a first heat radiating part contacting a side surface of the module substrate and the upper surface of the first heat sink, and a second heat radiating part bent from the first heat radiating part and contacting the second major surface of the module substrate, and arranged to the inside surface of the bottom cover, characterized in that the bottom cover further comprises a side portion; the light emitting module is arranged on the side portion of the bottom cover; a recess is provided in the lower portion of the bottom cover; the first heat radiating part of the second heat sink is inserted in the recess; and the upper surface of the first heat sink contacts the lower surfaces of both the first heat radiating part of the second heat sink and the bottom cover. a module substrate; and a light emitting element formed on a first major surface of the module substrate; a first heat sink arranged on the outer surface of the bottom cover; and a second heat sink being in contact with the first heat sink and the light emitting module, the second heat sink comprising: a first heat radiating part contacting a side surface of the module substrate and the upper surface of the first heat sink, and a second heat radiating part bent from the first heat radiating part and contacting the second major surface of the module substrate, and arranged to the inside surface of the bottom cover, characterized in that the bottom cover further comprises a side portion; the light emitting module is arranged on the side portion of the bottom cover; a recess is provided in the lower portion of the bottom cover; the first heat radiating part of the second heat sink is inserted in the recess; and the upper surface of the first heat sink contacts the lower surfaces of both the first heat radiating part of the second heat sink and the bottom cover. a first heat radiating part contacting a side surface of the module substrate and the upper surface of the first heat sink, and a second heat radiating part bent from the first heat radiating part and contacting the second major surface of the module substrate, and arranged to the inside surface of the bottom cover, characterized in that the bottom cover further comprises a side portion; the light emitting module is arranged on the side portion of the bottom cover; a recess is provided in the lower portion of the bottom cover; the first heat radiating part of the second heat sink is inserted in the recess; and the upper surface of the first heat sink contacts the lower surfaces of both the first heat radiating part of the second heat sink and the bottom cover.