Degradation degree table is a degradation degree table that describes a degradation degree of a secondary battery when the secondary battery is charged or discharged at a prescribed current rate with prescribed frequency. Degradation degree table describes the degradation degree in each of a plurality of state of charge (SOC) regions obtained through division of an SOC range of the secondary battery into the plurality of regions. Upper limit current determining part determines an upper limit current value to be used as a current rate at a time of charge or discharge, based on an estimated SOC and a target degradation degree with reference to degradation degree table.