The present invention is directed to a piezoelectric ink jet head wherein the partition walls that separate the adjacent recesses that make the pressure chambers are formed to have such a cross sectional shape as the width W.sub.1 in the planar direction at the upper end on the side of the substrate where the drive section is formed and height H in the direction of substrate thickness satisfy the expression (1): W.sub.1.gtoreq.H (1) while the width W.sub.1 and W.sub.2 of the lower end at the bottom of the recess of the substrate in the planar direction satisfy the expression (2): W.sub.1.ltoreq.W.sub.2 (2) in order to prevent the dot size and dot shape of the picture to be formed from varying as the state of driving the individual drive regions or the state of driving the individual piezoelectric elements are influenced by the state of driving the other plurality of drive regions or the state of driving the individual piezoelectric elements that surround the former.