To eliminate the fear of leaving a gap between mating faces of a plurality of element components assembled to form a microwave transmission circuit element.

A cross guide coupler 32 is composed of an upper and lower members 34, 36 and a coupling plate 38. A gold plating layer P on a mating side 34A of the upper member 34 and a gold plating layer P on an upper mating side of the coupling plate 38 are mated and pressed to compression-weld both gold plating layers. A gold plating layer P on a mating side 36A of the lower member 36 and a gold plating layer P on a lower mating side of the coupling plate 38 are mated and pressed to compression-weld both gold plating layers, thus forming the cross guide coupler 32.