The present invention relates to a band stop filter comprising: a resonating bar; a housing on the inside of which is formed a receiving space where the resonating bar is positioned, and which is made in a stepped form such that at least one part of an upper-end part is narrower than a lower-end part in terms of the internal width of the receiving space during the formation of the receiving space; a lower cover which has the resonating bar fitted thereto, is joined to the lower part of the housing and, when so joined, is assembled such that the resonating bar is inserted into the receiving space, and which forms the floor surface of the receiving space; and a hermetic-sealing cover which is provided within a recess pre-made in the housing in such a way as to couple with a resonator formed by the receiving space and the resonating bar on the inside of the receiving space, and is designed to hermetically seal the recess in the housing where a transmission line has been provided.