<p>This invention provides an optical element comprising a support substrate and a thin plate of a single crystal stacked on the support substrate through a thermoplastic adhesive. The optical element can easily regulate the phase of light waves and can restore the regulated state to the original state. The optical element comprises a support substrate (4) and a thin plate (1) of a single crystal stacked on the support substrate (4) through a thermoplastic adhesive (3) and is characterized in that the optical characteristics are regulated by, in such a state that the thermoplastic adhesive (3) is softened by heating the optical element, applying a stress of not more than the elastic limit to at least a part of the thin plate (1), forming a concave and convex part (10) in the thin plate (1), and then cooling the optical element to fix the concave and convex part (10).</p>
