An in-vehicle emergency power supply device comprising: a power storage unit including an electric double-layer capacitor; a charging circuit configured to charge the power storage unit; a discharging circuit configured to discharge the power storage unit; and a controller configured to control the charging circuit and the discharging circuit, wherein, when the controller causes the charging circuit to charge the power storage unit, the controller: is adapted to detect each of a plurality of values (V1, V2) of a voltage of the power storage unit at a plurality of time points (T1, T2) which are different from one another, each time point (T1, T2) corresponding to the passing of a respective one of a plurality of predetermined periods (PT1, PT2) from a starting of supplying power to the power storage unit by the charging circuit; is adapted to determine a set full charging voltage (Vu) of the power storage unit based on a rate of change of the voltage, the rate of change being obtained based on the plurality of values (V1, V2) of the voltage and the plurality of predetermined periods (PT1, PT2); is adapted to determine a correction charging voltage (Vc) lower than the set full charging voltage based on the set full charging voltage; and is adapted to cause the charging circuit to charge the power storage unit by operating the charging circuit until the voltage reaches the correction charging voltage. a power storage unit including an electric double-layer capacitor; a charging circuit configured to charge the power storage unit; a discharging circuit configured to discharge the power storage unit; and a controller configured to control the charging circuit and the discharging circuit, wherein, when the controller causes the charging circuit to charge the power storage unit, the controller: is adapted to detect each of a plurality of values (V1, V2) of a voltage of the power storage unit at a plurality of time points (T1, T2) which are different from one another, each time point (T1, T2) corresponding to the passing of a respective one of a plurality of predetermined periods (PT1, PT2) from a starting of supplying power to the power storage unit by the charging circuit; is adapted to determine a set full charging voltage (Vu) of the power storage unit based on a rate of change of the voltage, the rate of change being obtained based on the plurality of values (V1, V2) of the voltage and the plurality of predetermined periods (PT1, PT2); is adapted to determine a correction charging voltage (Vc) lower than the set full charging voltage based on the set full charging voltage; and is adapted to cause the charging circuit to charge the power storage unit by operating the charging circuit until the voltage reaches the correction charging voltage. is adapted to detect each of a plurality of values (V1, V2) of a voltage of the power storage unit at a plurality of time points (T1, T2) which are different from one another, each time point (T1, T2) corresponding to the passing of a respective one of a plurality of predetermined periods (PT1, PT2) from a starting of supplying power to the power storage unit by the charging circuit; is adapted to determine a set full charging voltage (Vu) of the power storage unit based on a rate of change of the voltage, the rate of change being obtained based on the plurality of values (V1, V2) of the voltage and the plurality of predetermined periods (PT1, PT2); is adapted to determine a correction charging voltage (Vc) lower than the set full charging voltage based on the set full charging voltage; and is adapted to cause the charging circuit to charge the power storage unit by operating the charging circuit until the voltage reaches the correction charging voltage.