A deterioration control device for a battery system comprising a plurality of battery cells and a charging and discharging control device controlling charging and discharging of the battery cells, the deterioration control device comprising: a utilization-record-data obtaining block configured to obtain utilization record data of the battery cell; a learning block configured to update an amount of data on a deterioration model parameter that indicates a deterioration state of the battery cell based on the utilization record data, to update the deterioration model parameter, and to output an updated result that is a deterioration rate table to the charging and discharging control device; and a learning instruction block configured to compare the utilization record data with an estimation value, to determine whether or not the deterioration model parameter is learnt, and to output a learning instruction signal to the learning block, while at the same time to calculate a change amount in the deterioration model parameter for the battery cell, and to output the change amount to the learning block; wherein the learning block comprises: a constant-current-capacity calculating unit configured to calculate a constant-current capacity value obtained by charging or discharging until a specific voltage at a constant current; a constant-voltage-capacity calculating unit configured to calculate a constant-voltage capacity value by outputting signals of charging and discharging the battery cell with the constant current until reaching the constant voltage, outputting signals of charging and discharging again the battery cell with a constant current which has a current value smaller than the constant current until reaching the constant voltage, repeating the output of said signals until the current value reaches a certain value, and integrating capacity values up to until the current value reached the certain value; and a current-capacity set calculating unit configured to calculate a set of the current value when the constant-voltage capacity value is obtained and the constant-voltage capacity value. a utilization-record-data obtaining block configured to obtain utilization record data of the battery cell; a learning block configured to update an amount of data on a deterioration model parameter that indicates a deterioration state of the battery cell based on the utilization record data, to update the deterioration model parameter, and to output an updated result that is a deterioration rate table to the charging and discharging control device; and a learning instruction block configured to compare the utilization record data with an estimation value, to determine whether or not the deterioration model parameter is learnt, and to output a learning instruction signal to the learning block, while at the same time to calculate a change amount in the deterioration model parameter for the battery cell, and to output the change amount to the learning block; wherein the learning block comprises: a constant-current-capacity calculating unit configured to calculate a constant-current capacity value obtained by charging or discharging until a specific voltage at a constant current; a constant-voltage-capacity calculating unit configured to calculate a constant-voltage capacity value by outputting signals of charging and discharging the battery cell with the constant current until reaching the constant voltage, outputting signals of charging and discharging again the battery cell with a constant current which has a current value smaller than the constant current until reaching the constant voltage, repeating the output of said signals until the current value reaches a certain value, and integrating capacity values up to until the current value reached the certain value; and a current-capacity set calculating unit configured to calculate a set of the current value when the constant-voltage capacity value is obtained and the constant-voltage capacity value. a constant-current-capacity calculating unit configured to calculate a constant-current capacity value obtained by charging or discharging until a specific voltage at a constant current; a constant-voltage-capacity calculating unit configured to calculate a constant-voltage capacity value by outputting signals of charging and discharging the battery cell with the constant current until reaching the constant voltage, outputting signals of charging and discharging again the battery cell with a constant current which has a current value smaller than the constant current until reaching the constant voltage, repeating the output of said signals until the current value reaches a certain value, and integrating capacity values up to until the current value reached the certain value; and a current-capacity set calculating unit configured to calculate a set of the current value when the constant-voltage capacity value is obtained and the constant-voltage capacity value.