A power supply system capable of inhibiting electricity loss and deterioration of each power supply device while realizing high stability in the case where electricity supply is performed by using a plurality of power supply devices is provided. A switching element corresponding to a power supply device having a higher inter-terminal voltage out of two power supply devices selectively becomes in ON state, and a switching element corresponding to a power supply device having a lower inter-terminal voltage selectively becomes in OFF state. Thereby, overload on a specific power supply device is prevented, and current flow between the different power supply devices is able to be prevented without generating needless electricity loss. Further, since electricity of the power supply device having a higher inter-terminal voltage is selectively outputted, variation between the respective power supply devices becomes allowable to some extent.