NOVELTY - The apparatus has an electric power transferring electric path (CL) which connects a power port i.e. connector (C1), to a power inverter circuit i.e. air conditioning inverter (IV4). An operating unit operates the power inverter circuit to supply electric power to a power supply unit and receives electric power from the power supply unit. A prohibiting unit prohibits the electric path between the power supply unit and the power inverter circuit from closing when the amount of charge of a capacitor (22) is equal to or less than a predetermined value.    USE - Power supply apparatus for vehicle i.e. parallel hybrid vehicle. Can also be used for a series hybrid vehicle, a parallel/series hybrid vehicle and an electric vehicle.    ADVANTAGE - The electric path between the power supply unit and the air conditioning inverter is prohibited from closing when the amount of charge of the capacitors is equal to or less than a predetermined value, so that a rush current can be prevented from passing from the power supply unit to the capacitors, and the reliability of the power supply and the electric system between the connector and the capacitors can be effectively prevented from decreasing. The electrical energy of a high-voltage battery is supplied to the capacitors via a high-resistance electric path before the electric path between the power supply unit and the air conditioning inverter is closed, so that the amount of charge of the capacitors can be appropriately increased. The electric power transferring relays are closed after the capacitors are charged, so that the electric path between the power supply unit and the air conditioning inverter can be safely closed. The power supply apparatus supplies electric power to a power supply unit or receives electric power from the power supply unit by using the air conditioning inverter, so that the required durability of the traction Motor/Generator (MG) inverter can be prevented from becoming excessive due to the transfer of the electric power. The common high-voltage battery is connected to the air conditioning inverter and the traction MG inverter, so that large discharged electric power and charged electric power can be obtained when supplying electric power to a power supply unit or receiving electric power from the power supply unit.    DESCRIPTION OF DRAWING(S) - The drawing shows a circuit diagram of a power inverter circuit.    Connector (C1, C2)    Electric power transferring electric path (CL)    Air conditioning inverter (IV4)    High-voltage battery (10)    Capacitors (22, 32, 42, 52)