To provide a diaphragm type piezoelectric actuator having a large displacing amount of a diaphragm easy to manufacture and a fast displacement of the diaphragm, and to provide a large and fast volumetric change of a cavity, a much injection amount of an ink in a small size by using the diaphragm type piezoelectric actuator.

The diaphragm type piezoelectric actuator comprises the diaphragm having a thin film-like substrate 21 and the thin film-like piezoelectric element 23 formed on the substrate 21, and divided electrodes mounted on upper and lower surfaces of the element 23 in such a manner that at least one is divided into a plurality of regions. Or directions of polarizations of the piezoelectric element are reverse to each other at a center and a peripheral edge of the diaphragm.