To provide a converter for a waveguide type dielectric filter that facilitates a coaxial waveguide conversion and which can easily be mounted.

An input output electrode 21 made of a conductor film is formed to the middle of one front side of a dielectric body 20, made of quartz glass or the like in the converter 20 formed to be fundamentally a rectangular solid and joined with an end of the waveguide type dielectric filter, and a dielectric body 22 is exposed around the input/output electrode 21. The dielectric body 22 is also exposed on one front side adjacent to the front side on which the input output electrode 21 is formed and the waveguide type dielectric filter is joined with this front side. A caption 23 indicates a grounding conductor film, that surrounds the input output electrode 21 via the exposed part of the dielectric body 22. A conductor film 23 is formed at an end of the surface, on which the input output electrode is formed in contact with a side on which the two front sides are in crossing. As shown in Figure 2, the conductor film may be formed over the entire circumference. A conductor film is formed on the other front sides. Moreover, in the case of employing the converter for an antenna input output of a duplexer, the dielectric body is exposed on two front sides opposed to each other and adjacent to the front side, on which the input output electrode is formed, and a transmitter side and a receiver side filters are respectively connected to the two front sides.