The state monitoring apparatus includes a high-voltage side monitoring section having monitoring units assigned to respective unit batteries and a low-voltage side monitoring section having a control device. The monitoring units measures the voltages of the unit batteries upon reception of a voltage measurement command transmitted from the control device, and determines whether or not the measured voltages are within a predetermined range. This determination is transmitted to the control device. If this determination is negative, the control device limits a charge/discharge current of the assembled battery, and then causes the monitoring units to transmit the measured voltages.