A dielectric resonator (10) having three surfaces formed by chamfering three ridged portions sharing an apex of a dielectric block and another three surfaces adjacent respectively thereto, in which each of the chamfered surfaces and the adjacent surfaces thereto offers an angle of 45 degrees and an area ratio of the chamfered surfaces with respect to the adjacent surfaces is 45% is mounted in a cut-off waveguide of a generally rectangular parallelopiped (21) and feeding probe (24) and (25) are provided for composing a dielectric filter.