Provided is a power supply device capable of preventing a drop in the voltage supplied to another machine that is connected aside from LED lighting devices, and continues driving the other machine. This power supply device is equipped with a plurality of LED drive circuits provided in parallel, corresponding respectively to a plurality of LED lighting instruments to drive each of the LED lighting instruments in a predetermined light-emission mode. The plurality of LED drive circuits and the other machine are connected to a DC supply unit having such constitution that a direct current power supply voltage is converted into a predetermined direct current voltage and supplied thereby. The power supply device is further provided with a constant current circuit whereof the input side is connected to the DC supply unit and the other machine, and the output side is connected to the plurality of LED drive circuits.