In a TM dual mode dielectric resonator apparatus including a cross-shaped TM dual mode dielectric resonator provided in an electrically conductive case, the cross-shaped dielectric resonator being comprised of first and second dielectric resonators, mode coupling means such as at least one groove or the like for coupling an operation of the first dielectric resonator with that of the second dielectric resonator is formed in the TM dual mode dielectric resonator. At least one first projection of a dielectric material for adjusting a coupling coefficient between the two dielectric resonators is formed on a portion of the crossing portion, wherein an adjustment amount of the coupling coefficient when the first projection is removed is previously determined. Further, respective at least one second and third projections of dielectric materials for adjusting resonance frequencies of the first and second dielectric resonators are formed respectively in a portion of the first dielectric resonator other than the crossing portion and in another portion of the second dielectric resonator other than the crossing portion.