The invention provides a piezoelectricity/electrostriction device which is capable of effectively preventing the vibration of a thin walled baffle portion from reducing and keeping high displacement (amplitude) and excellent responsiveness, and is capable of detecting high precision (high resolution and sensitivity). The invention is equipped with a frame thick wall portion (11) and a thin walledbattle portion (12), a ceramic matrix (1) of an empty cavity (13) and a piezoelectricity/electrostriction expansion device (2), wherein the ceramic matrix (1) of an empty cavity (13) which is communicated with an outer portion is formed through the thick wall portion (11) and the thin walled battle portion (12), and the piezoelectricity/electrostriction expansion device (2) comprises layer structures of a lower electrode (21), a piezoelectricity/electrostriction expansion film (22) and an upper electrode (23). Further, the outer side of the thin walled battle portion (12) is a convex arc, theinner portion of the piezoelectricity/electrostriction expansion device (2) residues a tensile stress F which is parallel to a fixed surface of the thin walled battle portion (12).