Dielectric filter and method of manufacturing the same

A dielectric filter includes a dielectric ceramic block (2) having a shape of a rectangular prism and having three or more through-holes (4a, 4b, 4c) formed in parallel; an inner conductor (5) covering the inner surface of each of the through-holes (4a, 4b, 4c) to thereby constitute the corresponding resonator (3a, 3b, 3c); an outer conductor (7) covering a predetermined outer surface of the dielectric ceramic block (2), excluding the open end surface (6); and input/output pads (9) formed on one side surface of the dielectric ceramic block (2) such that the pads (9) face resonators (3a, 3c) located at opposite ends. Each of the through-holes (4a, 4c) of the resonators (3a, 3c) located at the opposite ends is provided with a counterbore (8). An auxiliary conductor (11a) is disposed on the open end surface (6) to face at least one resonator (3b) excepting the resonators (3a, 3c) at the opposite ends. The auxiliary conductor (11a) surrounds the at least one resonator (3b) with an insulating gap formed therebetween and is connected to the outer conductor (7) on the side surface on which the input/output pads (9) are provided. The auxiliary conductor (11a) is preferably formed of a conductive material (16a) placed in a concave portion (14a) which has a pattern corresponding to the pattern of the auxiliary conductor (11a) and is formed on the open end surface (6).