Dielectric filter having forked auxiliary conductor

A dielectric filter includes a dielectric ceramic block having the shape of a rectangular prism and including three or more through-holes formed therein in parallel. An inner conductor covers the inner surface of each of the through-holes to form the corresponding resonator. An outer conductor covers a predetermined outer surface of the dielectric ceramic block, excluding the open end surface. Input/output pads are formed on one side surface of the dielectric ceramic block such that the pads face the two end resonators. Each of the through-holes of the end resonators is provided with a counterbore. An auxiliary conductor is disposed on the open end surface to face at least one intermediate resonator between end resonators. The auxiliary conductor at least partially surrounds the intermediate resonator with an insulating gap formed therebetween, and is connected to the outer conductor on the side surface on which the input/output pads are provided. The auxiliary conductor is formed by a conductive material disposed in a concave portion formed in the open end surface and having a pattern corresponding to the pattern of the auxiliary conductor.