A charge/discharge control method for an alkaline storage battery (11) includes: obtaining in advance a coefficient (K) representing characteristics of a memory effect of the alkaline storage battery; causing the alkaline storage battery to perform a charge/discharge between a lower-limit depth-of-charge (SOCb), of which a depth-of-charge is set within a range of 10% to 30%, and an upper-limit depth-of-charge (S), of which a depth-of-charge is set within a range of 70% to 90%; calculating an additional charge electricity quantity (C) based on the coefficient (K), the upper-limit depth-of-charge (S), and a predetermined reference time (T); measuring a charging/discharging time during which the alkaline storage battery performs the charge/discharge; and performing a charge of the alkaline storage battery with the calculated additional charge electricity quantity added to the upper-limit depth-of-charge, each time when the measured charging/discharging time reaches the reference time.