A power supply apparatus for an electrically powered vehicle, comprising: a main power storage device; a sub power storage device outputting a voltage lower than that of said main power storage device; a charging device operative in external charging for performing first power conversion to receive power from an external power supply and convert the received power into power charged to said main power storage device; characterized by a first switch (SCR1, SCR2) connected between a predetermined node (N1, N2) on an electric conduction path of said charging device in said first power conversion and said sub power storage device, and opened in said external charging, said charging device being configured such that when said external charging is not performed and said first switch (SCR1, SCR2) is closed said charging device performs second power conversion to receive power from said main power storage device and convert the received power via at least a portion of said electric conduction path into power to be charged to said sub power storage device and said charging device outputs the converted power on said predetermined node (N1, N2), wherein said charging device includes a first power conversion unit for performing alternating current/direct current voltage conversion from a first power line connected to said external power supply toward a second power line (152p, 152g), and a second power conversion unit for performing bidirectional direct current/direct current voltage conversion between a third power line (153p, 153g) connected to said main power storage device and said second power line (152p, 152g); said predetermined node (N1, N2) is provided on said second power line (152p, 152g); in said first power conversion, said first power conversion unit converts alternating current voltage on said first power line into direct current voltage and outputs the direct current voltage on said second power line (152p, 152g) and said second power conversion unit converts the direct current voltage on said second power line (152p, 152g) into voltage to be applied to charge said main power storage device and outputs the converted voltage on said third power line (153p, 153g); and in said second power conversion, said first power conversion unit is inactivated and said second power conversion unit receives voltage from said main power storage device on said third power line (153p, 153g), buck-boosts the received voltage to voltage to be applied to charge said sub power storage device, and outputs the buck-boosted voltage on said second power line (152p, 152g). a main power storage device; a sub power storage device outputting a voltage lower than that of said main power storage device; a charging device operative in external charging for performing first power conversion to receive power from an external power supply and convert the received power into power charged to said main power storage device; characterized by a first switch (SCR1, SCR2) connected between a predetermined node (N1, N2) on an electric conduction path of said charging device in said first power conversion and said sub power storage device, and opened in said external charging, said charging device being configured such that when said external charging is not performed and said first switch (SCR1, SCR2) is closed said charging device performs second power conversion to receive power from said main power storage device and convert the received power via at least a portion of said electric conduction path into power to be charged to said sub power storage device and said charging device outputs the converted power on said predetermined node (N1, N2), wherein said charging device includes a first power conversion unit for performing alternating current/direct current voltage conversion from a first power line connected to said external power supply toward a second power line (152p, 152g), and a second power conversion unit for performing bidirectional direct current/direct current voltage conversion between a third power line (153p, 153g) connected to said main power storage device and said second power line (152p, 152g); a first power conversion unit for performing alternating current/direct current voltage conversion from a first power line connected to said external power supply toward a second power line (152p, 152g), and a second power conversion unit for performing bidirectional direct current/direct current voltage conversion between a third power line (153p, 153g) connected to said main power storage device and said second power line (152p, 152g); said predetermined node (N1, N2) is provided on said second power line (152p, 152g); in said first power conversion, said first power conversion unit converts alternating current voltage on said first power line into direct current voltage and outputs the direct current voltage on said second power line (152p, 152g) and said second power conversion unit converts the direct current voltage on said second power line (152p, 152g) into voltage to be applied to charge said main power storage device and outputs the converted voltage on said third power line (153p, 153g); and in said second power conversion, said first power conversion unit is inactivated and said second power conversion unit receives voltage from said main power storage device on said third power line (153p, 153g), buck-boosts the received voltage to voltage to be applied to charge said sub power storage device, and outputs the buck-boosted voltage on said second power line (152p, 152g).