Ceramic cavities 1a and 1b have upper and lower open faces and contain dielectric cores 2a and 2b formed integrally therein. The ceramic cavities 1a and 1b are sandwiched between upper and lower panels 3 and 4 at the upper and lower open faces, respectively, of the ceramic cavities 1a and 1b via grounding plates 5a and 5b and grounding plates 6a and 6b, respectively, and the upper and lower panels 3 and 4 are fixed by screws. Based on this structure, a problem of an unreliable joint part between an open face of a ceramic cavity and a metal panel connected directly to each other by soldering and the problem of increase of the number of components of a structure in which a printed circuit board is mounted to the open face of the ceramic cavity by using grounding plates can be overcome, even when the ceramic cavity has an open face formed in a complex shape.