and each nozzle 48 and is open at an outer side of the piezoelectric plate member 41 the outer side being a side opposite to the ink chamber 45 further each inner groove 41 b is positioned in alignment with a contour of the ink chambers 45 and is open to the ink chamber 45 therefore highly flexible portion of the piezoelectric plate member 41 can be provided as a wall of the ink chamber 45 similar to the first embodiment each first electrode 42 has a u shape in cross section in conformance with the cross sectional shape of the inner groove 41 b and is positioned at the inner groove 41 b each first electrode 42 is exposed to the ink chamber 45 further each second electrode 43 also has a u shape in cross section in conformance with the cross sectional shape of the outer groove 41 a and is positioned at the outer groove 41 a length of the outer and inner grooves 41 a and 41 b are equal to each other each second electrode 43 is exposed to an outside further longitudinal positions of the outer and inner grooves 41 a and 41 b are coincident with each other in this embodiment each second electrode 43 are exposed to outside connection of a lead line to the second electrode 43 can be easily performed in operation while ink is filled in the ink chambers 45 a positive voltage is applied to a specific second electrode 43 while the first electrodes 42 remains grounded in this case linear expansion force is applied to the piezoelectric plate member 41 in the polarizing direction with.