A filter device includes a super-conducting type filters connected in
series with each other and is accommodated in a vacuum chamber. Operating
temperatures of the filters are controlled to different temperatures from
the outside of the vacuum chamber independently of each other. Each filter
varies its filtering characteristics, particularly its central frequency
of pass-band, in correspondence with the operating temperature, while
maintaining the same pass-band width. As the filters operated at the
different operating temperatures provide different filtering
characteristics, the combined or resulting filtering characteristics of
the filtering device can be adjusted as desired even after the filtering
device is installed at a mobile telecommunication base station.