PURPOSE: To make the coupling between long side vibration and short side vibration stable and to obtain a high accuracy temperature characteristic by forming integrally a support in the vicinity of a nodal point of the vibration generated at 3 division points of each side by a 3rd harmonic vibration.

CONSTITUTION: Let a size of a short side of a vibration section 1 be W and a size of a long side be L, then broken lines show one maximum displacement of the vibration of a 3rd harmonic wave, a vibration displacement UL is a long side vibration displacement and a vibration displacement UW is a short side vibration displacement. Four supports in parallel with the long side direction are formed integrally in the vicinity B of two nodal points near the middle among 3 division points of the end face of the long side vibration part. Thus, the coupling between the long side vibration and the short side vibration is made stable and a high accuracy temperature characteristic is obtained.