A control device of an electromotive vehicle that includes a motor (41, 42), a battery, an auxiliary, an electric power controller that controls electric power exchanged between the battery and the auxiliary and a charger that carries out external charging in which a power supply outside the vehicle is used to charge the battery, comprising: a first control unit that, during drive control of the vehicle, controls the electric power generated by the motor (41, 42) so that an SOC that is a ratio of an actual amount of charge to a full charge capacity of the battery falls within a predetermined range by controlling the electric power controller; and a second control unit that, when the power supply is connected to the vehicle, controls the electric power controller and the charger so as to carry out extended charging in which a variation in the SOC during the external charging is larger than a width of the predetermined range; characterized by a calculating unit that calculates the full charge capacity by multiplying a ratio of a maximum value of the SOC to a variation in the SOC during the extended charging by an accumulated value of current flowing into the battery from start of the extended charging to end of the extended charging, wherein when the power supply is connected to the vehicle, the second control unit carries out first discharging in which the battery is discharged until the SOC decreases to a first SOC that falls within a first range lower than a lower limit value of the predetermined range, starts the extended charging after the first discharging is ended, and ends the extended charging at the time when the SOC has reached a second SOC that falls within a second range higher than an upper limit value of the predetermined range, the battery has a characteristic such that a variation in the SOC with respect to a unit variation in voltage of the battery in the first and second ranges is smaller than a variation in voltage of the SOC with respect to a unit variation in voltage of the battery in the predetermined range, the control device further comprising a voltage sensor that detects a voltage of the battery, wherein the calculating unit calculates an SOC at the time when the extended charging is started on the basis of an output from the voltage sensor at the time when the extended charging is started, calculates an SOC at the time when the extended charging is ended on the basis of an output from the voltage sensor at the time when the extended charging is ended, and calculates a difference between the calculated SOC at the time when the extended charging is started and the calculated SOC at the time when the extended charging is ended as a variation in the SOC during the extended charging. a first control unit that, during drive control of the vehicle, controls the electric power generated by the motor (41, 42) so that an SOC that is a ratio of an actual amount of charge to a full charge capacity of the battery falls within a predetermined range by controlling the electric power controller; and a second control unit that, when the power supply is connected to the vehicle, controls the electric power controller and the charger so as to carry out extended charging in which a variation in the SOC during the external charging is larger than a width of the predetermined range; characterized by a calculating unit that calculates the full charge capacity by multiplying a ratio of a maximum value of the SOC to a variation in the SOC during the extended charging by an accumulated value of current flowing into the battery from start of the extended charging to end of the extended charging, wherein when the power supply is connected to the vehicle, the second control unit carries out first discharging in which the battery is discharged until the SOC decreases to a first SOC that falls within a first range lower than a lower limit value of the predetermined range, starts the extended charging after the first discharging is ended, and ends the extended charging at the time when the SOC has reached a second SOC that falls within a second range higher than an upper limit value of the predetermined range, the battery has a characteristic such that a variation in the SOC with respect to a unit variation in voltage of the battery in the first and second ranges is smaller than a variation in voltage of the SOC with respect to a unit variation in voltage of the battery in the predetermined range, the control device further comprising a voltage sensor that detects a voltage of the battery, wherein the calculating unit calculates an SOC at the time when the extended charging is started on the basis of an output from the voltage sensor at the time when the extended charging is started, calculates an SOC at the time when the extended charging is ended on the basis of an output from the voltage sensor at the time when the extended charging is ended, and calculates a difference between the calculated SOC at the time when the extended charging is started and the calculated SOC at the time when the extended charging is ended as a variation in the SOC during the extended charging.