PURPOSE: To keep surely electric insulation between terminals by cutting preliminarily threes parts, a flexible substrate, a back side electrode and a piezoelectric ceramic diaphragm so as to form a very shallow cutting slot onto the piezoelectric ceramic diaphragm not to cause cutting chip.

CONSTITUTION: The piezoelectric ceramic diaphragm 8 and the flexible board 9 are bonded by an adhesives 10. Then the shallow cutting slot 11 is formed by the preliminary cutting to the substrate 9, the back side electrode 3 and the diaphragm 8 so as to connect the back side electrode 3 dividedly to each electric terminal 2 formed on the substrate 9. The face of the back side electrode 3 and the diaphragm 8 are bonded on an ultrasonic wave absorbing body 7. Then the surface electrode 4 and the diaphragm 8 are cut at the position in matching with the preliminary cutting position so as to form a cutting slot 6 reaching the halfway of the thickness of the diaphragm 8.