A dielectric resonator has a metallic casing having an opening, a metallic cover which covers the opening, and a dielectric resonance element having a pair of flat surfaces formed opposite from each other, one of the pair of flat surfaces being brought into contact with a bottom portion of the casing. At least one of the cover and the bottom portion has a resilient portion which supports the dielectric resonance element and presses one of the pair of flat surfaces by a biasing force so as to follow expansion or contraction of the dielectric resonance element due to a change in temperature. The biasing force applied from the resilient portion is obtained by warping of a portion of the cover or a portion of the bottom portion that one of the pair of flat surfaces or an edge portion of the flat surface contacts.