A circuit unit connects outputs from a first power supply and a second power supply in parallel, and simultaneously supplies powers from both power supplies to a load. A control unit controls an output current from the first power supply to an upper-limit value or lower, and controls an output current from the second power supply to a value obtained by subtracting the upper-limit value from a current detected by a current detector. An abnormality detector detects an abnormality in simultaneously supplied power, based on a reference current value associated with an operating state of the power supply apparatus and the current detected by the current detector.