A bus bar module is attached to a battery assembly having a plurality of single cells which are assembled to each other along a first direction. The bus bar module includes a circuit body, a bus bar, and a holder. The circuit body includes a main line that extends in the first direction, a branch line that extends from the main line so as to branch from the main line, and a connection portion provided in a position close to a distal end of the branch line rather than a folded portion of the branch line and configured to be connected to the bus bar.