A battery pack comprising two or more battery modules stacked in a first direction, each battery module comprising: a cell assembly having a plurality of secondary batteries; and a module housing having a rectangular parallelepiped shape and including an upper wall, a lower wall, a left wall, and a right wall, regarded in the direction of stacking of the battery modules, to accommodate the cell assembly in an inner space defined by the module housing and having at least one cooling channel embedded in at least one wall, characterized in that the at least one cooling channel is embedded in the left wall and/or the right wall, wherein the battery modules further comprise at least one channel connection member for connecting the at least one cooling channel each to at least one cooling channel of another battery module, wherein the at least one channel connection member is located at the front end or the rear end, or at both ends of the sidewall (303, 304) of the module housing in a front and rear direction regarded in the stacking direction of the modules, and wherein each channel connection member includes: a connection tube partially inserted into and connected to the cooling channel of the battery module; and a stopper having a hollow structure to surround an outer surface of the connection tube, wherein the stopper is configured to protrude upward, downward, leftward, rightward from the connection tube, regarded in the first direction, so as to block the end surface of the module housing to prevent the connection tube from being inserted into the cooling channel beyond an appropriate range while the connection tube is being inserted into the cooling channel. a cell assembly having a plurality of secondary batteries; and a module housing having a rectangular parallelepiped shape and including an upper wall, a lower wall, a left wall, and a right wall, regarded in the direction of stacking of the battery modules, to accommodate the cell assembly in an inner space defined by the module housing and having at least one cooling channel embedded in at least one wall, characterized in that the at least one cooling channel is embedded in the left wall and/or the right wall, wherein the battery modules further comprise at least one channel connection member for connecting the at least one cooling channel each to at least one cooling channel of another battery module, wherein the at least one channel connection member is located at the front end or the rear end, or at both ends of the sidewall (303, 304) of the module housing in a front and rear direction regarded in the stacking direction of the modules, and wherein each channel connection member includes: a connection tube partially inserted into and connected to the cooling channel of the battery module; and a stopper having a hollow structure to surround an outer surface of the connection tube, wherein the stopper is configured to protrude upward, downward, leftward, rightward from the connection tube, regarded in the first direction, so as to block the end surface of the module housing to prevent the connection tube from being inserted into the cooling channel beyond an appropriate range while the connection tube is being inserted into the cooling channel. a connection tube partially inserted into and connected to the cooling channel of the battery module; and a stopper having a hollow structure to surround an outer surface of the connection tube, wherein the stopper is configured to protrude upward, downward, leftward, rightward from the connection tube, regarded in the first direction, so as to block the end surface of the module housing to prevent the connection tube from being inserted into the cooling channel beyond an appropriate range while the connection tube is being inserted into the cooling channel.