To provide a power supply device capable of starting charging to a main capacitor after the light emission of an illuminator even when synchronization signals from a camera can not be used.

The power supply device 1 is provided with a power supply 10, supplies power obtained from the power supply to the illuminator which emits illumination light, and includes a boosting circuit 13 for outputting a charging voltage to the illuminator by boosting the power supply voltage of the power supply, an electromagnetic wave detection portion for detecting electromagnetic waves generated in the illuminator, and a boosting control portion 18 for starting the supply of the power supply voltage to the boosting circuit when the electromagnetic waves at or above a prescribed level are detected in the electromagnetic wave detection portion and making the boosting circuit execute the boosting operation.