A piezoelectric substance has a multi-layer structure consisting of single crystal layers or uniaxial crystal layers of a perovskite oxide expressed by the general formula of ABO.sub.3 in which a main component at the site (A) is Pb, and a main component at the site (B) includes at least three elements selected from the group consisting of Mg, Zn, Sc, In, Yb, Ni, Nb, Ti and Ta. The multi-layer structure comprises a first crystal phase layer having any crystal structure selected from the group consisting of tetragonal, rhombohedral, pseudocubic, orthorhombic and monoclinic crystals; a second crystal phase layer having a different crystal structure from the crystal structure of the first crystal phase layer; and a boundary layer between the first crystal phase layer and the second crystal phase layer, and having a crystal structure gradually changing in a thickness direction of the layer.