PURPOSE: To reduce undesired thickness longitudinal vibration with good productivity by forming a slot to a flat plate forming by press processing, splitting the forming and giving a taper to the thickness of the circumference of the vibrator.

CONSTITUTION: A flat plate forming body 5 made of a piezoelectric ceramic material is formed by extrusion forming or sheet forming. A pressure is exerted to the forming body 5 from both faces by using a press metallic mold to process the slot 6. Then sintering processing, electrode provision and polarization processing are applied to the plate, then the plate is cut and split to form a piezoelectric ceramic resonator 7. In such a case, the taper 8 is formed to the thickness of the circumference of each resonator 7 after cutting by the slot 6. Thus, the thickness is ununiformized and undesired thickness longitudinal vibration is reduced.