PURPOSE: To attain the elimination of moisture in space in the inside of a supporting base through a through hole in a very short time by forming the cylindrical through hole connecting the inner and outer parts to the supporting base.

CONSTITUTION: The dielectric resonator 6 having a strong dielectric constant is adhered onto a base 7 made of a dielectric ceramic at both end faces of the cylindrical supporting base 12 via adhesives 9, 10 in the inside of the case 1. Four notches 13 are formed to an end face adhered to the base 7 of the supporting base 12 and form a through hole connecting the inside and the outside of the cylindrical supporting base after the adhesion. Through the constitution above, the moisture in the case 1 after the completion is absorbed in a moisture absorbent 2 through the through hole 5 thereby being decreased. Thus, the moisture of the space 14 in the inside of the supporting base 12 is also absorbed quickly through the through hole 13, the water content included in the adhesives 9, 10 is also extracted toward the cylindrical outside and inside and dehydrated from both sides, then extracted very quickly.