A power supply system includes power storage units formed of battery assemblies, respectively, converters corresponding to the power storage units, respectively, and a charger receiving an electric power from an external power supply for externally charging the power storage units. An ECU estimates an SOC of each power storage unit based on the SOC of a battery block of the smallest SOC in the power storage unit. When the power storage unit attains a state allowing charging by the external power supply, the ECU controls the corresponding converter to charge the power storage unit with the charge current supplied from the charger, and derives, for each power storage unit, a charge-allowed power based on the SOC of the battery block of the largest SOC. When a total value of the derived charge-allowed powers of the respective power storage units is equal to or smaller than an actual value of the supply power supplied from the external power supply, the ECU ends the external charging of the power storage units.