A liquid jetting head using a piezoelectric element that is capable of obtaining sufficient displacement through the application of a driving voltage is provided. In the liquid jetting head, which comprises a substrate formed with a pressure chamber, a diaphragm formed on the substrate, and a piezoelectric thin film element formed on the diaphragm, the diaphragm bends in convex form toward the pressure chamber side, and the amount by which the diaphragm bends is no more than 0.4% of the width of the pressure chamber.