A battery module is provided with a plurality of batteries (10) joined in a straight-line configuration, insulating caps (30) that insulate the series connected batteries (10), and connecting hardware (20, 40) disposed between connected batteries (10) that connect those batteries in series. The insulating cap (30) has an outer insulating region (31) that covers outer surfaces of adjacent batteries (10) connected in series. The connecting hardware (20, 40) has a first welding section (21, 41) that is welded to the end-plane electrode (19) of one battery, a second welding section (22, 42) that is disposed outside the first welding section and is welded to the end-plane electrode of another battery (10), and welding terminals (23, 43) that are disposed outside the outer insulating region (31) of the insulating cap (30) at battery outer surfaces in a manner insulated by the outer insulating region (31).