In order to easily detect a disconnection in a lowest-order voltage detection line when a voltage detection circuit for detecting the respective voltage of a plurality of serially connected cells is made redundant, the operation power supply of a first voltage detection circuit and a second voltage detection circuit is fed from both ends of a plurality of serially connected cells. The lowest node of the plurality of cells and the first voltage detection circuit are connected by the two lines of a voltage detection line and a negative power supply line. The lowest node of the plurality of cells and the second voltage detection circuit are connected by a single wire serving as both of a voltage detection line and a negative power supply line.