PURPOSE: To enhance a peel resistance to vibration and to transmit the displacement of a piezoelectric element to a vibration plate more efficiently.

CONSTITUTION: In a method wherein a piezoelectric element 7 is bonded on the surface of a conductive vibration plate or an insulating vibration plate 6 provided with an electrode surface layer 9, a film of a coupling agent 11 is formed on the surface of the vibration plate 6 as a first process, the piezoelectric element 7 is bonded on the film with an insulating adhesive 10 as a second process, and the process is completed after the adhesive is cured.