A backlight assembly (700; 704; 705) comprising: a lamp emitting light an optical plate and an optical sheet layer adjusting optical properties of the emitted light; a lamp socket (400; 401; 402) into which the lamp is inserted and the lamp socket being inserted in a socket insertion hole which is provided along at least one side of the bottom surface of a bottom chassis (200; 205); and a side mold (300, 380; 301; 304) having at least one portion of a bottom surface thereof opened, the side mold (300, 380; 301; 304) comprising a supporting portion supporting the optical plate 130 and the optical sheet layer thereon, a side wall (320; 324; 215) formed at one side of the supporting portion, a sloping portion (330; 334) extending from a lateral end of the supporting portion and a top surface of the sloping portion (330; 334) being inclined downwardly at an angle, and at least one socket connection portion (370; 620) receiving the lamp socket (400; 401; 402), wherein the lamp socket (400; 401; 402) includes a lamp connection portion (410; 411), a power connection portion, and a light blocking plate preventing the lamp socket from being overly inserted within the side mold and positioned at an interface between the lamp connection portion (410; 411) and the power connection portion, the light blocking plate protruded outward outside with respect to the lamp connection portion (410; 411) and the power connection portion, and wherein the lamp is inserted into the lamp connection portion (410; 411) and the power connection portion is connected to an inverter printed circuit board providing power to the lamp; characterized in that a guide groove is disposed in the lamp socket so that the lamp is received therein from above. a lamp emitting light an optical plate and an optical sheet layer adjusting optical properties of the emitted light; a lamp socket (400; 401; 402) into which the lamp is inserted and the lamp socket being inserted in a socket insertion hole which is provided along at least one side of the bottom surface of a bottom chassis (200; 205); and a side mold (300, 380; 301; 304) having at least one portion of a bottom surface thereof opened, the side mold (300, 380; 301; 304) comprising a supporting portion supporting the optical plate 130 and the optical sheet layer thereon, a side wall (320; 324; 215) formed at one side of the supporting portion, a sloping portion (330; 334) extending from a lateral end of the supporting portion and a top surface of the sloping portion (330; 334) being inclined downwardly at an angle, and at least one socket connection portion (370; 620) receiving the lamp socket (400; 401; 402), wherein the lamp socket (400; 401; 402) includes a lamp connection portion (410; 411), a power connection portion, and a light blocking plate preventing the lamp socket from being overly inserted within the side mold and positioned at an interface between the lamp connection portion (410; 411) and the power connection portion, the light blocking plate protruded outward outside with respect to the lamp connection portion (410; 411) and the power connection portion, and wherein the lamp is inserted into the lamp connection portion (410; 411) and the power connection portion is connected to an inverter printed circuit board providing power to the lamp; characterized in that a guide groove is disposed in the lamp socket so that the lamp is received therein from above.