Inner-conductor holes whose internal surfaces are coated with inner conductors are provided in a dielectric block. Input/output electrodes are provided on the outside of the dielectric block, coupled to the inner conductors by electrostatic capacitance. Gap portions are provided between the input/output electrodes and an outer conductor. The input/output electrodes may be formed to extend from a bottom surface (mounting surface) and onto a side surface of an external surface of the dielectric block. Filter characteristics are determined depending on a width or a depth of the gap portion on the side surface of the dielectric block.