To provide an illumination apparatus utilizing microwave that releases further effectively the heat generated by the internal apparatus by making the casing a heat sink and has a cooling structure capable of sealing so that the outside foreign matters may not enter inside.

The illumination apparatus comprises a magnetron 20, an electric bulb part 50 emitting light by microwave, a waveguide 40 that couples the magnetron 20 and the electric bulb part 50 and transmits the microwave generated by the magnetron 20 to the electric bulb part 50, and a casing 10 that accommodates the magnetron 20 and the waveguide 40 and is jointed to the electric bulb part 50. The casing 10 is closely contacted to the outside of the magnetron 20 for releasing the heat generated by the magnetron 20 and accommodates the magnetron 20.