PURPOSE: A state managing apparatus and the equalizing method of electric storage devices are provided to equalize capacity charged and discharged in multiple electric storage devices by estimating the SOC value of an electric storage device based on the time change rate of an electric storage device. CONSTITUTION: A voltage measuring unit measures the voltage of each electric storage device individually. A time measuring unit(42) measures a time difference from a time in which the time change rate of the voltage of any one electric storage device reaches a reference value to a time in which the time change rate of the voltage of another electric storage device reaches a reference value. A discharge unit individually discharges the each electric storage device. An equalization controlling unit(44) controls the discharge unit by using the time difference. [Reference numerals] (18) Charger/load; (22) Ammeter; (24) Voltmeter; (26) Discharge circuit; (28) Thermometer; (32) Memory; (42) Time measuring unit; (44) Equalization controlling unit; (46) Deterioration determining unit; (AA) Program; (BB) Reference value(K); (CC) Reference time(KT); (DD) Corresponding table; (EE) Discharge time(HT)