A manufacturing method for a multi-nozzle ink jet head using piezoelectric elements. The head has a nozzle member in which a plurality of nozzles are formed, a pressure chamber wall member in which a plurality of pressure chambers are formed, and piezoelectric type actuators that have a diaphragm and a plurality of piezo elements and apply pressure to each of the plurality of pressure chambers for ejecting ink from the nozzles. A coating member having high rigidity is provided on inner surfaces of the pressure chamber walls or on parts of the diaphragm in contact with the pressure chamber wall member, thus increasing the rigidity of the pressure chamber walls.