A power supply device (10) is provided with a plurality of constant current output circuits (14) that are capable of supplying power to a load (12). Each constant current output circuit (14) is provided with: a pulse generation unit (20) for generating a pulse voltage with a pulse width corresponding to a voltage and current that are to be output; and a proportional-integral (PI) feedback control unit (30) for performing feedback control on the pulse voltage outputted by the pulse generation unit (20) in such a manner that a load current achieves a prescribed value. If an abnormality occurs in the constant current output circuit (14) that is supplying power to the load (12), and the constant current output circuit (14) that is to supply power to the load is switched, the power supply device (10) sets the feedback control cycle for the pulse generation unit (20) integrated in the constant current output circuit (14) of the switching destination to a second cycle that is higher than a first cycle in the pre-switched constant current output circuit (14).