A control module is arranged side by side with a battery module. The control module includes positive and negative electrode bus bars which are electrically connected to positive and negative electrode input/output terminals of the battery module, respectively. The bus bars are mounted in a mounting part. The mounting part has first and second control-side ventilation holes through which air flows onto first and second battery stacks, respectively, in the battery module. The mounting part has notches in which at least one of the positive electrode bus bar and the positive input/output terminals and at lease one of the negative electrode bus bar and the negative input/output terminals are formed. The first and second control-side ventilation holes are arranged side by side in the lateral direction. The notches, the positive electrode bus bar, and the negative electrode bus bar are located between the first and second control-side ventilation holes.