An ink jet head includes a base member having a plurality of openings, a diaphragm formed on a surface of the base member covering each of the openings, a pressure chamber being formed at each of the openings, and a plurality of piezoelectric elements formed at locations on the diaphragm corresponding to the pressure chambers, each of the piezoelectric elements being configured to eject liquid from a corresponding pressure chamber by causing deformation of the diaphragm. The diaphragm includes a plurality of stress release portions that reduces compressive residual stress in the diaphragm, each of the stress release portions corresponding to one of the piezoelectric elements.