A charge/discharge condition adoptable in a secondary battery of high-temperature operation type is calculated by a small amount of calculations. A resource matrix includes a plurality of state indicators and a plurality of charge/discharge conditions. The resource matrix is referred to and two or more state indicators related to an input state indicator so as to satisfy a condition are selected from the plurality of state indicators. A charge/discharge condition corresponding to each of the two or more selected state indicators are extracted from the plurality of charge/discharge conditions, so that two or more charge/discharge conditions are extracted. Interpolation is performed in the two or more selected state indicators and the two or more extracted charge/discharge conditions, so that a charge/discharge condition adoptable in a secondary battery in a case where a state of the secondary battery is indicated by the input state indicator, is calculated.