To obtain a relational expression between the size of a resonating electrode which is capable of increasing the maximum value Qimax of Q of electrical resonance necessary for oscillation as a ceramic resonator, and the electrode without spurious that disturbs main vibration, in thickness longitudinal higher harmonic vibration of which a frequency constant is great from 4,000 to 5,000 Hzm, in a single board piezoelectric substrate with a bismuth layered structure ferroelectric body as a main crystal structure.

In a piezoelectric device including a single piezoelectric substrate with a bismuth layered structure ferroelectric body as a main crystal structure and at least a pair of vibrating electrodes which face each other on both principal surfaces of the piezoelectric substrate, thickness longitudinal higher harmonic vibration of which a frequency constant is 4,000 to 5,000 HzM, is used inside the vibrating electrode and when a vibrating electrode area is defined as S and electrode distance is defined as (t), the condition of 2.5≤S1/2/t≤8 is satisfied.