A battery pack, comprising: a pack housing including a lower frame and a side frame; and one or more battery modules accommodated in the pack housing, wherein the battery module includes: a plurality of cell stacks in which a plurality of battery cells are stacked in a first direction; and a plurality of end plates fastened to the lower frame, and wherein the plurality of end plates and the plurality of cell stacks are alternately disposed in the first direction, wherein the side frame includes a guide block that blocks spreading of high-temperature and highpressure gas or flame generated in one portion of the battery module to other portions of the battery module or other battery modules, and protrudes in a second direction perpendicular to the first direction, wherein at least one of the plurality of end plates includes an insertion groove into which the guide block is inserted, wherein a venting passage having at least a portion extending in the first direction is formed in the side frame, wherein the side frame includes a plurality of openings communicating with the venting passage and an internal space of the pack housing, and wherein the guide block is disposed between the plurality of openings. a pack housing including a lower frame and a side frame; and one or more battery modules accommodated in the pack housing, wherein the battery module includes: a plurality of cell stacks in which a plurality of battery cells are stacked in a first direction; and a plurality of end plates fastened to the lower frame, and wherein the plurality of end plates and the plurality of cell stacks are alternately disposed in the first direction, wherein the side frame includes a guide block that blocks spreading of high-temperature and highpressure gas or flame generated in one portion of the battery module to other portions of the battery module or other battery modules, and protrudes in a second direction perpendicular to the first direction, wherein at least one of the plurality of end plates includes an insertion groove into which the guide block is inserted, wherein a venting passage having at least a portion extending in the first direction is formed in the side frame, wherein the side frame includes a plurality of openings communicating with the venting passage and an internal space of the pack housing, and wherein the guide block is disposed between the plurality of openings. a plurality of cell stacks in which a plurality of battery cells are stacked in a first direction; and a plurality of end plates fastened to the lower frame, and wherein the plurality of end plates and the plurality of cell stacks are alternately disposed in the first direction, wherein the side frame includes a guide block that blocks spreading of high-temperature and highpressure gas or flame generated in one portion of the battery module to other portions of the battery module or other battery modules, and protrudes in a second direction perpendicular to the first direction, wherein at least one of the plurality of end plates includes an insertion groove into which the guide block is inserted, wherein a venting passage having at least a portion extending in the first direction is formed in the side frame, wherein the side frame includes a plurality of openings communicating with the venting passage and an internal space of the pack housing, and wherein the guide block is disposed between the plurality of openings.