A power supply apparatus for a vehicle, comprising: first and second power storage devices ( B1, B2) provided electrically in parallel to a main load ( 14, 22); a first power converter provided between said first power storage device and said main load (14, 22); a second power converter provided between said second power storage device and said main load ( 14, 22); a third power converter receiving a current divided from a path connecting said first power converter and said first power storage device; an auxiliary load driven by power from said third power converter; a controller controlling said first to third power converters ( 12A, 12B, 33); a current sensor detecting a charging/discharging current for said first power storage device; characterized in that the power supply apparatus further comprises a battery charger for charging said first and second power storage devices ( B1, B2) by power received from a source external to the vehicle; wherein said battery charger is connected to said first power storage device, and said first and second power converters ( 12A, 12B) are configured to divide part of a current received from said battery charger to operate as another battery charger charging said second power storage device; and said controller is configured to determine charging/discharging currents for said first and second power storage devices ( B1, B2) reflecting variations in a current flowing through said auxiliary load to control said first power converter and/or second power converter such that the determined currents are charged/discharged, and to suspend said third power converter temporarily to calculate a current divided toward said third power converter based on the difference in the charging/discharging current for said first power storage device before and after the suspension, and to correct an operation of said first and second power converters (12A, 12B) based on said divided current, said first power converter is configured to boost a voltage from said first power storage device toward said main load (14, 22) during charging from the source external to the vehicle, and said second power converter is configured to operate such that a constant current flows from said main load ( 14, 22) toward said second power storage device during charging from the source external to the vehicle. first and second power storage devices ( B1, B2) provided electrically in parallel to a main load ( 14, 22); a first power converter provided between said first power storage device and said main load (14, 22); a second power converter provided between said second power storage device and said main load ( 14, 22); a third power converter receiving a current divided from a path connecting said first power converter and said first power storage device; an auxiliary load driven by power from said third power converter; a controller controlling said first to third power converters ( 12A, 12B, 33); a current sensor detecting a charging/discharging current for said first power storage device; characterized in that the power supply apparatus further comprises a battery charger for charging said first and second power storage devices ( B1, B2) by power received from a source external to the vehicle; wherein said battery charger is connected to said first power storage device, and said first and second power converters ( 12A, 12B) are configured to divide part of a current received from said battery charger to operate as another battery charger charging said second power storage device; and said controller is configured to determine charging/discharging currents for said first and second power storage devices ( B1, B2) reflecting variations in a current flowing through said auxiliary load to control said first power converter and/or second power converter such that the determined currents are charged/discharged, and to suspend said third power converter temporarily to calculate a current divided toward said third power converter based on the difference in the charging/discharging current for said first power storage device before and after the suspension, and to correct an operation of said first and second power converters (12A, 12B) based on said divided current, said first power converter is configured to boost a voltage from said first power storage device toward said main load (14, 22) during charging from the source external to the vehicle, and said second power converter is configured to operate such that a constant current flows from said main load ( 14, 22) toward said second power storage device during charging from the source external to the vehicle.