Providing a power supply system having a plurality of power supply apparatuses connected in parallel to each other, each of which is not affected by a voltage fluctuation of a reverse flow-preventive diode provided in an output line thereof, and can provide a stable output voltage controlled with high accuracy. Each of the power supply apparatuses includes a positive output terminal 33 connected to a load 13, a reverse flow-preventive diode 31 connected to the positive output terminal 33, a VF correcting circuit 46 for detecting a forward voltage of the reverse flow-preventive diode 31 and providing a controlling unit with the detected voltage in a feedback manner, an output current detecting/correcting circuit 45 for detecting a forward current of the reverse flow-preventive diode 31 and providing the controlling unit with the detected current in a feedback manner, and the controlling unit for controlling the anode potential of the reverse flow-preventive diode 31. The controlling unit controls the transformer 24 by the switching operation so that the anode potential of the reverse flow-preventive diode 31 remains constant, and drops the anode potential in accordance with the forward current of the reverse flow-preventive diode 31, and raises the anode potential in accordance with the forward voltage of the reverse flow-preventive diode 31.