A power-supply apparatus includes a power-supply circuit to which an input voltage and an input current are input, to include a switching element to be controlled by a control signal so as to generate an output voltage and an output current, a memory, and a processor coupled to the memory and the processor to calculate a first duty ratio of the control signal so that the output voltage approaches a target voltage, calculate a second duty ratio of the control signal for the switching element, based on the input voltage, the input current, the output voltage, and the output current, detect deterioration of the power-supply circuit, based on the first duty ratio and the second duty ratio, generate the control signal of the first duty ratio when the power-supply circuit has not deteriorated, and generate the control signal for stopping the power-supply circuit when the power-supply circuit has deteriorated.