A power supply device comprises: a voltage converting portion that converts a voltage generated from a power supply portion into an output voltage to be supplied to a load; a voltage divider circuit that generates an output voltage setting signal for providing a set value of the output voltage; a set value changeover portion that turns on/off set value changeover switches to change a voltage divider ratio of the voltage divider circuit to change the set value; a storage device that stores a state appropriate for each set value changeover switch for keeping the value of the output voltage within a specified range; a set value changeover switch control portion that controls the set value changeover switches so as to bring each set value changeover switch into a state as stored in the storage device when the voltage is supplied from the voltage converting portion to the load; and an output voltage control portion that controls the voltage converting portion so as to make zero a deviation between the value of the output voltage and the set value.