The present invention relates to a battery device which uses a bus bar to connect a plurality of batteries in a simple structure manner and realizes temperature equalization of the batteries. In the battery device, the bus bar is utilized to connect batterys of a plurality of battery array groups. The battery device includes a bus bar having a coupling bus bars, a positive electrode bus bar and a negative electrode bus bar. The coupling bus bar includes: a positive electrode connection member arranged to sequentially connect positive electrode terminals of the respective batteries included in one battery array group; and a negative electrode connection member arranged to sequentially connect negative electrode surfaces of the respective batteries included in another battery array group. The positive electrode connection member is electrically connected with the negative electrode connection member. The positive electrode bus bar is arranged to sequentially connect specific positive electrode terminals. The negative electrode bus bar is arranged to sequentially connect specific negative electrode terminals.