A power supply apparatus for supplying power to an electric load (3) through a power supply line includes power source means (101) which supplies electric power through the power supply line, a capacitor (105) connected to the power supply line which extends from the power source means (101), a charge circuit (106) which receives power from the power source means (101) and outputs a current value to charge the capacitor (105), detecting means (121) which detects a voltage value of the capacitor (105), first determination means (122) which determines whether charge of the capacitor (105) is complete based on the voltage detected by the detecting means (121), and second determination means (122) which determines, in the case that the first determination means determines that the charge of the capacitor (105) is complete, whether the voltage detected by the detecting means (121) is equal to or smaller than a threshold value to determine whether an error occurs.