A battery system includes a battery module that is constituted with a plurality of serially connected battery cells, a plurality of integrated circuits that group the battery cells so as to perform processing on battery cells in each group, a first transmission path through which a command signal is transmitted via a first insulating circuit from a higher-order control circuit that controls the integrated circuits to a highest-order integrated circuit of the integrated circuit, a second transmission path through which a data signal collected by the integrated circuits is transmitted from the highest-order integrated circuit to a lowest-order integrated circuit, and a third transmission path through which the data signal is transmitted from the lowest-order integrated circuit to the higher-order control circuit via a second insulating circuit.