Disclosed herein are a bus bar for connecting two or more devices to an external circuit, wherein the bus bar is capable of equalizing internal resistances between a connection point of the external circuit and connection points of the respective devices, and a middle- or large-sized battery pack including the same. The bus bar according to the present invention reduces the difference of internal resistances due to a circuit to allow a battery module having optimized performance and a middle- or large-sized battery pack including the same to be manufactured.