An ink droplet jet device in which the volume of the ink channels is varied by deformation of the side walls due to piezoelectric thickness shear mode to thereby jet an ink droplet requires sufficient volume variation of the ink channels to function reliably. To satisfy this requirement, the material and thickness of an adhesive agent used to secure the piezoelectric plate to the cover plate is selected so that the value obtained by dividing Young's modulus of adhesive agent for adherence between the upper surface of the side wall of the piezoelectric plate and the cover plate by the thickness of the adhesive agent is above 5 X 10³ kg/mm³, preferably 5 X 10⁴ kg/mm³, and more preferably above 1.2 X 10⁵ kg/mm³. Further, the material and thickness of the adhesive agent is selected so that the value obtained by dividing Young's modulus of the adhesive agent for adherence between the end surface of the side wall and the nozzle plate by the thickness of the adhesive agent is below 1 X 10⁶ kg/mm³, preferably 5 X 10⁵ kg/mm³, and more preferably 3 X 10⁵ kg/mm³. By these settings, the jet velocity of the ink droplet is above a predetermined value, and stable ink droplet jetting can be performed.