A piezoelectric/electrostrictive device is formed with a connecting plate, a diaphragm, and a substrate which are mutually joined. A joining direction of the connecting plate with the substrate and a joining direction of the connecting plate with the diaphragm are mutually intersected to form a cross. The diaphragm is straddled between the connecting plate and the substrate. A piezoelectric element is arranged on a surface of the diaphragm, and the diaphragm is convexly curved in a direction perpendicular to the two directions forming the cross. The piezoelectric/electrostrictive device is an element for converting electrical energy into mechanical energy such as a mechanical displacement, force or vibrations. Conversely, the piezoelectric/electrostrictive device may be employed to convert mechanical energy into electrical energy, as well as improve the operational characteristics thereof.