A dielectric duplexer includes a substantially rectangular dielectric block. The dielectric block includes inner-conductor-containing holes each having an inner conductor on the inner surfaces thereof, and inner-conductor-unformed portions on which the inner conductors are not formed are formed in the vicinity of first ends of the inner-conductor-containing holes. The dielectric block further includes an outer conductor and input/output electrodes which are formed on the outer surface thereof, and the input/output electrodes are separated from the outer conductor. A through-hole having a short circuited electrode formed on the inner surface thereof is provided between two of the inner-conductor-containing holes so as to run from the mounting surface to the surface opposite thereto.