Abstract: An illumination apparatus used by connecting an illumination head to a power source device, capable of supplying a rated current to individual light emitting devices of the illumination head by using a power source device of an identical rating irrespective of the specification of the illumination head, wherein the illumination head has a current detection resistor for detecting current flowing through the power supply circuit, and the resistance value of the resistor is selected so as to cause a voltage drop equal with a predetermined reference potential when a rated current is supplied to each of the light emitting devices, and the power source device is provided with a current controller for controlling the supplied current such that the potential for the voltage drop caused by the current detection resistor is equal with the reference potential.