A radio frequency electric power conversion mechanism of the present invention includes a circuit board including a fiber reinforced resin board, instead of an expensive ceramic circuit board. The radio frequency electric power conversion mechanism has a combined configuration of a plurality of fiber reinforced resin boards laminated to each other with a conductive foil therebetween, a via hole array made of an electric conductor passing through the boards, a transmission line closely adhered to the surface of a board, and a waveguide having a notch in a part of the waveguide on the aperture side. The radio frequency electric power conversion mechanism further has other structural features.