The piezoelectric resonator of this invention consists of a piezoelectric ceramic plate which is polarized in the direction of thickness over the entire plate, two split electrodes are formed on one main surface of the piezoelectric ceramic plate, and an electrode is formed on the entire main surface opposed to the above main surface on which are formed the split electrodes. When an operating voltage is supplied to the above two split electrodes, the piezoelectric ceramic plate between the two split electrodes and the other electrode undergoes resonance in a thickness dilatational mode with a phase difference of 180.degree..