Management device and power supply system

A management device comprising:

• a voltage measurement circuit that measures a voltage of each of a plurality of cells connected in series;
• a plurality of voltage measurement lines that connect between nodes of the plurality of cells and voltage measurement terminals of the voltage measurement circuit;
• a lower reference potential line that connects between a lower node of a lowermost cell of the plurality of cells and a lower reference terminal of the voltage measurement circuit;
• a voltage dividing resistor that is connected between a predetermined fixed potential and a lowermost voltage measurement line among the plurality of voltage measurement lines;
• and
• a controlling circuit that monitors a voltage between a voltage dividing point potential of the voltage dividing resistor and a lower reference potential of the voltage measurement circuit and diagnoses presence or absence of disconnection of the lowermost voltage measurement line or the lower reference potential line.