The invention provides a technology for equalization charge and discharge of a plurality of secondary batteries.(BMS 20)is a device performing management of the state of a plurality of secondary batteries (50) in a serial connection,and is provided with:a voltmeter separately measuring voltage valves V of the secondary batteries (50), a discharge circuit (26) separately performing discharge of the secondary batteries (50), and an equalization control part (44) controlling the discharge circuit, when the voltage valve V of each secondary battery (50) reaches a reference voltage in charge and discharge, the equalization control part (44) makes discharge of the secondary battery (50) be started. According to the (BMS 20), compared with the condition that discharge of the secondary battery (50) as a target is started after the voltage valves V of the other secondary batteries (50) reach the reference voltage, discharge start time of the secondary battery (50) as the target is earlier.