PURPOSE: To improve quality and production efficiency by constituting two constituting elements in such a manner that one thereof is thinner than the other constituting element at the optical axis of the lens, the surface of the thinner constituting element is optically finished coarse and a binder has the same refractive index.

CONSTITUTION: The first and second lens constituting elements 10, 12 are so formed as to have the mutually coincident surfaces 16, 18 and both of these surfaces 16, 18 are the surfaces of revolution. At least one thereof is composed of a synthetic plastic material and is so polished as to be made thinner at the optical axis than the other lens constituting element. The polished and mutually coincident surface of the one lens constituting element is bonded to the other mutually coincident surfaces 16, 18 in the optically rough state by using the binder 21 having the same or nearly the same refractive index as the refractive index of the thinner lens material of the first and second lens constituting elements 10, 12. As a result, the thinner constituting element of the two constituting elements may be polished from the relatively thick plastic blank and is hardly subjected to strain during cooling at the time of production.