Within a range of a second limit current (±I_adj_max) set based on the performance of a secondary battery (140), a charging and discharging control device (170) determines an upper limit value (I_adj_limit) or a lower limit value (−I_adj_limit) of a state of charge (SOC) adjustment current (I_adj) in accordance with load power (required power and regeneration power) of a vehicle (100). Using an adjustment logic determined based on these limit values of the SOC adjustment current (I_adj), the charging and discharging control device (170) also determines the SOC adjustment current (I_adj) corresponding to an actually measured SOC value of the secondary battery (140).