PURPOSE: To form an optical element equivalent to an optical element having non-plane and aspherical functional surfaces easily with a high precision by forming both faces of optical materials into plane or spherical surfaces and giving a refractive index distribution to these surface layers and polishing them into plane or spherical surfaces.

CONSTITUTION: For example, both faces of optical materials are formed into plane or spherical surfaces, and the refractive index distribution where the refractive index value accords with the depth is given to surfaces layers of optical materials by ion exchange or the like. Both faces of optical materials are polished into plane or spherical surface to form functional surfaces as optical faces. An ion exchange layer different by the length from the optical axis is formed on surface layers of the optical element obtained in this manner.