To provide a piezoelectric device which can increase and decrease a frequency.

A piezoelectric device (100) of a first aspect is a piezoelectric device which houses a tuning-fork piezoelectric vibration chip (50) in a package (PKG). The tuning-fork piezoelectric vibration chip (50) includes a base part (23) formed of a piezoelectric material, a pair of vibration arms (21) extending in parallel in a predetermined direction from the base part, and a frequency adjusting part (26) formed on the tip side of the vibration arm. The package (PKG) has an insulating material part (56) on the internal face (BT) of the package irradiated with a laser beam (L). The frequency adjusting part (26) has a metal film (28a) which extends in a predetermined direction and an electrode non-forming part (29a) which extends in a predetermined direction so that a laser beam can transmit and on which a metal film is not formed.