A power supply apparatus includes a power source unit supplying power to an electric load through a power supply line, a capacitor connected to the power supply line, a charge circuit charging the capacitor while restricting a current value of the power supplied from the power source unit, a detection unit detecting a voltage value of the capacitor, a controller which switches, after the charge of the capacitor is completed, a current value of the charge circuit to a first current value smaller than a current value supplied before the charge of the capacitor is completed, a first determination unit determining whether a first condition is satisfied based on the voltage value detected by the detection unit after the charge of the capacitor is completed, and a second determination unit determining whether an error process is to be performed based on a determination result of the first determination unit.