Abstract: The present invention provides a 3-dimensional wave-guiding structure for horn or tube-type waveguides. The wave-guiding structure comprises a fiber-reinforced composite material and a conductive nonwoven fabric shaped together with the composite material. The present invention also provides a 3-dimensional wave-guiding structure comprising a conductive nonwoven fabric 30 and a fiber-reinforced triaxial woven fabric 20 which are laminated alternately or in an arbitrary order. The conductive nonwoven fabric having flexibility can be readily shaped together with the composite material composed of a triaxial woven fabric or the like in conformity with the 3-dimensional shape of various horn or tube-like waveguides such as a waveguide diplexer, waveguide circulator, hybrid waveguide and waveguide directional coupler to provide a lightweight wave-guiding structure capable of achieving both excellent mechanical and electrical characteristics.