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 communication unit (34) for sending and receiving drive information, which is required to drive the pulse generation unit (20), to and from the other constant current output circuit (14). 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 to the other constant current output circuit (14), the other constant current output circuit (14) will drive the pulse generation unit (20) by using the drive information received via the communication unit (34). Thus, even if the power supply means for supplying power to the load is switched, the power supply device (10) is able to provide the power outputted by the power supply means of the switching destination as the power required by the load in a shorter period of time.