A power supply apparatus for vehicles is provided. This apparatus includes a battery mounted on a vehicle as well as first and second power transferring means and a power conversion unit. The first power transferring means transfers power between the battery and a first power supply section placed outside the vehicle, in a state where the battery is electrically connected to the power supply section. The second power transferring means transfers power between the battery and the power supply section placed outside the vehicle, in a state where the battery is electromagnetically connected to a second power supply section. The power conversion unit is used commonly in both the first and second power transferring means and used for transferring the power between the battery and the first power supply section and for transferring the power between the battery and the second power supply section.