To provide a cooling system of an illumination apparatus utilizing microwave that effectively releases the heat generated from the internal exothermic apparatus by fitting a heat exchanger formed of a flowing passage of the coolant on the outside part of the internal exothermic apparatus, and has a cooling structure sealed so that the outside foreign matter may no enter inside.

The illumination apparatus having a magnetron 31, an electric bulb part 50 emitting light by microwave, and a waveguide 33 comprises a heat exchanger 60 fitted on the outside part of the magnetron 31 and for which a flow passage of coolant is formed, a radiation part 40 that is installed on the outside of a casing 51 and radiates heat of the coolant heated going through the passage of the heat exchanger 60, and a flow generating means 10 that is installed between the exit of the radiation part 40 and the entrance of the heat exchanger 60 and circulates the coolant to the heat exchanger 60 and the radiation part 40.