An automotive power supply system comprising: a battery module that includes a plurality of electrically and serially connected battery groups (GB1-GBN) each constituted with a plurality of electrically and serially connected battery cells (BC1-BC4); a plurality of integrated circuits (3A-3N) each disposed in correspondence to one of the battery groups; a control circuit; a signal transmission path between the plurality of integrated circuits and the control circuit; and a relay circuit for controlling supply of power from the battery module, wherein: in response to a start signal instructing an operation start and received via the signal transmission path when the relay circuit is open, each integrated circuit is adapted to executing measurement of terminal voltages and an abnormality diagnosis at the battery cells in the corresponding battery group, holding the measurement result of the terminal voltages, and transmitting the result of the abnormality diagnosis to the control circuit via the signal transmission path; and the control circuit is adapted to verifying whether or not an abnormality has occurred at each battery cell of the plurality of battery groups based upon the result of the abnormality diagnosis transmitted from the integrated circuits, controlling the relay circuit so that the relay circuit is closed and the power is supplied from the battery module if it is verified that no abnormality has occurred at each battery cell of the plurality of battery groups, and receiving the measurement result of the terminal voltages held and transmitted from the integrated circuits via the signal transmission path after the relay circuit has closed and the power has supplied from the battery module. a battery module that includes a plurality of electrically and serially connected battery groups (GB1-GBN) each constituted with a plurality of electrically and serially connected battery cells (BC1-BC4); a plurality of integrated circuits (3A-3N) each disposed in correspondence to one of the battery groups; a control circuit; a signal transmission path between the plurality of integrated circuits and the control circuit; and a relay circuit for controlling supply of power from the battery module, wherein: in response to a start signal instructing an operation start and received via the signal transmission path when the relay circuit is open, each integrated circuit is adapted to executing measurement of terminal voltages and an abnormality diagnosis at the battery cells in the corresponding battery group, holding the measurement result of the terminal voltages, and transmitting the result of the abnormality diagnosis to the control circuit via the signal transmission path; and the control circuit is adapted to verifying whether or not an abnormality has occurred at each battery cell of the plurality of battery groups based upon the result of the abnormality diagnosis transmitted from the integrated circuits, controlling the relay circuit so that the relay circuit is closed and the power is supplied from the battery module if it is verified that no abnormality has occurred at each battery cell of the plurality of battery groups, and receiving the measurement result of the terminal voltages held and transmitted from the integrated circuits via the signal transmission path after the relay circuit has closed and the power has supplied from the battery module. in response to a start signal instructing an operation start and received via the signal transmission path when the relay circuit is open, each integrated circuit is adapted to executing measurement of terminal voltages and an abnormality diagnosis at the battery cells in the corresponding battery group, holding the measurement result of the terminal voltages, and transmitting the result of the abnormality diagnosis to the control circuit via the signal transmission path; and the control circuit is adapted to verifying whether or not an abnormality has occurred at each battery cell of the plurality of battery groups based upon the result of the abnormality diagnosis transmitted from the integrated circuits, controlling the relay circuit so that the relay circuit is closed and the power is supplied from the battery module if it is verified that no abnormality has occurred at each battery cell of the plurality of battery groups, and receiving the measurement result of the terminal voltages held and transmitted from the integrated circuits via the signal transmission path after the relay circuit has closed and the power has supplied from the battery module.