To provide structure of a guidehorn or various kinds of waveguides which keep mechanical strength and are excellent in electrical characteristics, by integrating with composite materials.

This guidehorn or waveguide is constituted by conductive non- woven fabric formed with fiber reinforced composite materials, especially by reinforced fiber of three-axis textile 20 and conductive non-woven fabric 30 laminated alternately or in an arbitrary order as composite materials. Since the conductive non-woven fabric is flexible, it can be formed easily, integrated, along the solid shape of diplexers, circulators, hybrids and directional couplers as a guidehorn or various kinds of waveguides made of composite materials constituted of three-axis textile and the like. Also, it is light-weighted and can achieve a structure excellent both in mechanical strength and in electrical characteristics.