PURPOSE: To make satisfactory a characteristic of a sound field and remove a mutual interference of respective piezoelectric members by providing grooves crossing over both main surfaces of piezoelectric plates, forming plural rows of protrusions and providing electrodes on the surface of the protrusions.

CONSTITUTION: A piezoelectric member 9 made of, for example lead titanate zirconate has one main surface on which the grooves 10 are disposed in a direction of Y axis in a depth of about 70% with respect to the thickness (t) of the piezoelectric member 9 and the protrusions 11 are disposed and the other main surface on which a groove 12 of the same depth is disposed in a direction of X axis and the protrusions 13 are formed. On the main surface side of the protrusions 11, 13, electrodes 14, 15 are formed and in the grooves 10, 12, a resin such as epoxy resin having a different acoustic impedance value from the piezoelectric member is filled as a reinforcing material 16. A central area in the direction of the thickness is physically separated and independent from an adjacent part. The piezoelectric part on which the electrodes 14, 15 are crossed can be considered to be an independent oscillator and the mutual interference of the respective piezoelectric parts is prevented and the characteristic of the sound field of the ultrasonic wave is not destroyed.