A power supply system that includes a converter that converts an input alternating-current voltage into a direct-current voltage and outputs the direct-current voltage to a load. The system includes a switcher that electrically connects one of multiple alternating-current power supplies to the converter, a voltage detector that detects an input voltage input to the converter, and a current detector that detects an output current output from the converter. The switcher repeats, for a predetermined amount of time, a determination of whether there is an abnormality in alternating-current power supply based on the input voltage detected by the voltage detector. Moreover, if there is an abnormality, the switcher switches which alternating-current power supply is connected to the converter. Further, the switcher adjusts, based on the result of detection by the current detector, the amount of time for which the determination is performed.