Abstract: The present invention can couple multiple resonances through a change in the shape of a part of a dielectric resonance element or of a cavity so as to couple energy between resonances when generating the multiple resonances, such as dual or triple resonances, of the dielectric resonance element in one cavity, thereby simplifying the shape and reducing the size thereof. In addition, a dielectric resonance element is manufactured into the shape of a doughnut so as to generate triple resonances in one cavity, thereby facilitating the manufacture of the dielectric resonance element and the emission of heat from the dielectric resonance element.