A battery system includes a battery block, a cooling pipe, and a coolant feeding device. The battery block includes a plurality of rectangular batteries that have a width greater than a thickness and are securely arranged in array alignment by a battery holder. The cooling pipe cools the rectangular batteries of the battery block. The coolant feeding device feeds coolant to the cooling pipe. In the battery system, the cooling pipe is arranged on the surface of the battery block in a thermally-coupled state so that the rectangular batteries are cooled by the coolant, which is circulated through the cooling pipe.