An assembled battery total voltage detection circuit includes a main control circuit, a divider resistor connected between a plus terminal and a minus terminal of an assembled battery insulated from the main control circuit, and a differential amplifier circuit that amplifies voltage divided by the divider resistor. A constant electric potential relative to a ground of the main control circuit is applied to a midpoint of the divider resistor. The main control circuit measures the voltage divided by the divider resistor via the differential amplifier circuit.