A dielectric waveguide filter includes resonators in a dielectric plate. A main coupling portion is between a final stage resonator of a first set and an initial stage resonator of a second set. A trap resonator is between a resonator that is one stage before the final stage resonator of the first set and a resonator that is one stage after the initial stage resonator of the second set, and the trap resonator is coupled to the final stage resonator of the first set and the initial stage resonator of the second set.