BATTERY PACK

According to the present invention, a battery pack containing a cell stack including one or more battery cells, including a pack case having a space in which the cell stack is placed, the pack case including: a base plate supporting a lower portion of the cell stack; a main wall extending across the base plate and coupled to a center portion of the base plate; a side wall having a hollow shape and including a gas venting path therein, and coupled along a periphery of an edge of the base plate; and a plurality of supplementary wall having a front end coupled to the main wall, and a rear end coupled to the side walls, wherein the supplementary wall includes a first partition member including a pair of ribs formed to extend along a longitudinal direction of the supplementary wall, and a second partition member coupled to the first partition member, and the battery pack characterized in that at least one of the first partition member and the second partition member includes a first hole between the ribs included in the first partition member.