There is provided a voltage monitoring apparatus for monitoring an output voltage of an assembled battery. The voltage monitoring apparatus comprises: voltage monitoring sections, each section monitoring a voltage of each block of the plurality of blocks into which the plurality of unit cells are divided, wherein the voltage monitoring sections are connected one another through communication lines; and a control unit which is connected to the voltage monitoring section through the communication lines. The voltage monitoring section compares the respective detected voltages of the unit cells with the threshold voltage to determine a result of the comparison, and transmits the comparison result to the control unit. In a case where the threshold voltage is changed, the control unit transmits a registration signal indicating the changed threshold voltage, and when received the registration signal, the voltage monitoring section changes the stored threshold voltage to the changed threshold voltage.