<p>A piezoelectric body (14) comprises a piezoelectric layer (26), an upper electrode (28) formed on one side of the piezoelectric layer (26) facing a plate member (12), and a lower electrode (30) formed on the other side of the piezoelectric layer (26). A part of the piezoelectric body (14) is so displaced as to get closer to or away from the plate member (12) by applying an electric field between a first upper electrode (28a) and a first lower electrode (30a) in a driving region (32), by applying an electric field between a second upper electrode (28b) and a second lower electrode (30b) in a supporting region (34), or by applying electric fields both between the first upper electrode (28a) and first lower electrode (30a) in the driving region (32) and between the second upper electrode (28b) and second lower electrode (30b) in the supporting region (34).</p>
