A method of working a piezoelectric substance, which comprises the steps of, forming, on one surface of a piezoelectric block, an etching mask having an aperture which defines a boundary region between a first piezoelectric segment to be removed, and a second piezoelectric segment to be left remained, forming, on the opposite surface of the piezoelectric block, a sacrificial layer which corresponds to the first piezoelectric segment to be removed and the boundary region, etching the piezoelectric block in the boundary region to reach the sacrificial layer, and eliminating the sacrificial layer to remove the first piezoelectric segment.