A metal oxide layer is disposed on the lower potential side when an electric field in a predetermined direction is applied to the piezoelectric body which is deformed by an applied electric field, and compensates for the oxygen vacancies which are generated in the piezoelectric body by applying the electric field. A second metal oxide layer is disposed on the higher potential side of the electric field applied to the piezoelectric body, and by applying an electric field in the direction reverse to the electric field, compensates for the oxygen vacancies which are accumulated in the piezoelectric body, thus degradation of the piezoelectric characteristic of a piezoelectric element can be repaired.