The step of forming an electrode for external connection applies a conductive resin (10) to one end portion of each of a plurality of ink chambers (26) within each of the ink chambers (26) and to the top surface of each of a plurality of protrusions over a piezoelectric substrate (60) in one line perpendicular to the direction in which the ink chambers (26) extend. Subsequently, the conductive resin (10) located on the top surface of each of the plurality of ink chamber partitions is removed by polishing or grinding. As a result, the conductive resin (10) filling a space within each ink chamber (26) constitutes an electrode for external connection. This allows the capacitance due to the piezoelectric substrate to be decreased. Further, the driving frequency of the ink jet head can be increased. Thus, an ink jet head and its manufacturing method can be provided with a reduced power consumption, with an increased productivity and reliability and that allows a high speed printing.