To combine the members easily in a casing without incorporating a piezoelectric element in a plunger.

In a piezoelectric actuator where a plunger, a spring member for normally urging the plunger so that the distal end thereof projects from the opening of a casing, a piezoelectric element for converting a voltage signal into a mechanical displacement, and an operation piece connected to the free end of the piezoelectric element and engaging with the plunger disengageably under control of the long piezoelectric element are incorporated in a casing, the operation piece is guided in horizontal or vertical state by a guide means provided in the casing and engages with the plunger disengageably, the piezoelectric element includes a first piezoelectric element and a second piezoelectric element having one end coupled with one end of the first piezoelectric element and capable of spreading outward from the free end side, the proximal end of the first piezoelectric element is supported on the casing side, and the operation piece is arranged at the free end of the second piezoelectric element.