A small in-band-flat-group-delay type dielectric filter having low-loss characteristics with a small amplitude deviation and uniform-group-delay frequency characteristics is obtained, which enables broad-band characteristics to be obtained easily. The in-band-flat-group-delay type dielectric filter includes a plurality of dielectric coaxial resonators 14, 15, a coupling circuit comprising a combination of reactive elements, with which the dielectric coaxial resonators 14, 15 are coupled to one another, and input/output terminals 11 connected to ends of the coupling circuit. The dielectric coaxial resonators 14 coupled to the input/output terminals 11 are allowed to have a different characteristic impedance from that of the interstage dielectric coaxial resonators 15.