A compact dielectric resonator apparatus is comprised of a dielectric block having a plurality of mutually parallel throughholes formed therethrough with inner surfaces covered with a conductive film so as to provide coaxial resonators. The degree of coupling between a mutually adjacent pair of such dielectric resonators can be adjusted by forming grooves, a bottomed hole or a slit or burying a conductive plate therebetween in the dielectric block, and varying physical characteristics of such grooves, bottomed hole, slit and/or conductive plate, without changing the separations between the throughholes or the external dimensions of the dielectric block.