The present invention provides a filter exhibiting excellent filter characteristics and having less number of stages. A dielectric substrate (1) has one surface connected to a top conductor (2) and an opposite surface connected to a bottom conductor (3). A pair of rows of via-holes connecting together the top conductor (2) and the bottom conductor (3) are formed along the signal transfer direction. A slit (6) is formed in a portion of the top conductor (2) overlying the central resonator among a plurality of resonators. The slit (6) extends in a direction perpendicular to the signal transfer direction. Slits (7, 8) are formed in each of portions of the top conductor (2) overlying resonators disposed at both ends. A coplanar waveguide (9) mounted on the top conductor (2) is connected to the slit (7).