A battery control device for controlling a secondary battery, comprising: a current measuring part for measuring charge/discharge current value of the secondary battery; a discharge capacity calculator for integrating the charge/discharge current value measured by said current measuring part so as to calculate calculated value of a discharge capacity in the secondary battery, and correcting the calculated value of the discharge capacity in the secondary battery charged/discharged to a depth of discharge at which the calculated value of the discharge capacity is corrected; an estimated error calculator for calculating an estimated error of the calculated value of the discharge capacity calculated by said discharge capacity calculator; a first comparator for setting the secondary battery where the estimated error calculated by said estimated error calculator exceeds a first threshold as a candidate for correction of the calculated value of the discharge capacity, a first threshold holding part for holding the first threshold; a bidirectional converter for controlling charge/discharge of the secondary battery; and a charge/discharge command part for causing said bidirectional converter to charge/discharge all or some of the secondary battery as the candidate for the correction of the calculated value of the discharge capacity to the depth of discharge at which the correction is made, wherein at least one of (i), (ii) and (iii) applies: (i) said estimated error calculator calculates the estimated error including a factor that becomes larger as a correcting amount in a previous correction of the calculated value of the discharge capacity is larger; (ii) said estimated error calculator calculates the estimated error including a factor that becomes larger as a change over time in the charge/discharge current value measured by said current measuring part is larger; (iii) said estimated error calculator calculates the estimated error including a factor that becomes larger as the charge/discharge current value measured by said current measuring part is larger. a current measuring part for measuring charge/discharge current value of the secondary battery; a discharge capacity calculator for integrating the charge/discharge current value measured by said current measuring part so as to calculate calculated value of a discharge capacity in the secondary battery, and correcting the calculated value of the discharge capacity in the secondary battery charged/discharged to a depth of discharge at which the calculated value of the discharge capacity is corrected; an estimated error calculator for calculating an estimated error of the calculated value of the discharge capacity calculated by said discharge capacity calculator; a first comparator for setting the secondary battery where the estimated error calculated by said estimated error calculator exceeds a first threshold as a candidate for correction of the calculated value of the discharge capacity, a first threshold holding part for holding the first threshold; a bidirectional converter for controlling charge/discharge of the secondary battery; and a charge/discharge command part for causing said bidirectional converter to charge/discharge all or some of the secondary battery as the candidate for the correction of the calculated value of the discharge capacity to the depth of discharge at which the correction is made, (i) said estimated error calculator calculates the estimated error including a factor that becomes larger as a correcting amount in a previous correction of the calculated value of the discharge capacity is larger; (ii) said estimated error calculator calculates the estimated error including a factor that becomes larger as a change over time in the charge/discharge current value measured by said current measuring part is larger; (iii) said estimated error calculator calculates the estimated error including a factor that becomes larger as the charge/discharge current value measured by said current measuring part is larger.