A backlight assembly and a liquid crystal display device can discharge heat from the lamp unit to the outside or effectively dissipate the heat. The backlight assembly of the present invention includes a lamp unit, a receiving member for receiving the lamp unit, a first heat dissipation member disposed below the receiving member, and a second heat dissipation for wrapping around a lateral side of the receiving member and the first heat dissipation member. The lamp unit is disposed on an area corresponding to the lateral side of the receiving member. In one embodiment, the first heat dissipation member is a flat plate made of graphite and disposed on an outer side of the bottom of the receiving member. The second heat dissipation member is metal with good thermal conductivity in close contact with the first heat dissipation member and the lateral side of the receiving member where the lamp unit is disposed. Thus, the heat discharged from the lamp unit can be distributed uniformly over the entire area of the receiving member. In addition, the lateral side of the receiving member where the lamp unit is disposed can be replaced with the second heat dissipation member.