A power supply apparatus for a vehicle for delivering and receiving electric power to and from an electric load installed on a vehicle, comprising: a first power storage device; a first positive bus (PL1B) connected to a positive electrode of said first power storage device; a first negative bus connected to a negative electrode of said first power storage device; a first power converter provided between said electric load and a first pair of buses made up of said first positive bus (PL1B) and said first negative bus; a second power storage device; a second positive bus (PL1C) connected to a positive electrode of said second power storage device; a second negative bus connected to a negative electrode of said second power storage device; and a second power converter provided between said first pair of buses and a second pair of buses made up of said second positive bus (PL1C) and said second negative bus, a controller for controlling said first power converter and said second power converter, wherein said first power storage device includes a battery, said second power storage device includes a plurality of series-connected capacitors, characterized in that said second power converter is configured to be operable so that a voltage between said first pair of buses is boosted higher than or equal to a voltage between said second pair of buses, said first power converter is configured to be operable so that a voltage provided on said electric load is boosted higher than or equal to the voltage between said first pair of buses, a withstand voltage of said plurality of series-connected capacitors is lower than a maximum voltage between said first pair of buses, said controller is configured to: (a) determine a request value that is lower than or equal to a total of each of available input/output range (PB, PC) of said first and second power storage devices corresponding to a detected temperature, (b) cause said second power storage device to input/output power corresponding to said request value to/from said second power storage device when said request value is smaller than or equal to said available input/output range of said second power storage device, and (c) cause said second power storage device to input/output power corresponding to an upper limit of said available input/output range to/from said second power storage device and to input/output power corresponding to the difference between said request value and said upper limit to/from said first power storage device when said request value exceeds said available input/output range of said second power storage device. a first power storage device; a first positive bus (PL1B) connected to a positive electrode of said first power storage device; a first negative bus connected to a negative electrode of said first power storage device; a first power converter provided between said electric load and a first pair of buses made up of said first positive bus (PL1B) and said first negative bus; a second power storage device; a second positive bus (PL1C) connected to a positive electrode of said second power storage device; a second negative bus connected to a negative electrode of said second power storage device; and a second power converter provided between said first pair of buses and a second pair of buses made up of said second positive bus (PL1C) and said second negative bus, (a) determine a request value that is lower than or equal to a total of each of available input/output range (PB, PC) of said first and second power storage devices corresponding to a detected temperature, (b) cause said second power storage device to input/output power corresponding to said request value to/from said second power storage device when said request value is smaller than or equal to said available input/output range of said second power storage device, and (c) cause said second power storage device to input/output power corresponding to an upper limit of said available input/output range to/from said second power storage device and to input/output power corresponding to the difference between said request value and said upper limit to/from said first power storage device when said request value exceeds said available input/output range of said second power storage device.