Provided is a management device (BMS 40) for an assembled battery 30 which uses a positive electrode active material containing lithium iron phosphate and having an electrically conductive layer formed on a surface thereof, the BMS 40 being provided with: a current sensor 43 which measures a current flowing through the assembled battery 30; a voltage sensor 45 which measures a voltage of the assembled battery 30; and a management unit 42. When a state in which the current value measured by means of the current sensor 43 is less than a reference value is defined as a pause state of the assembled battery 30, the management unit 42, when the assembled battery 30 has entered the pause state, performs: a discharge process (S101) for causing the assembled battery 30 to discharge; a post-discharge measurement process (S102) for measuring the voltage by means of the voltage sensor 45 after the assembled battery 30 has been discharged in the discharge process; and a first estimation process (S103) of estimating the SOC of the assembled battery 30 on the basis of the voltage measured in the post-discharge measurement process and OCV-SOC characteristics 62 after the discharge.