A method for producing a composite mirror. It comprises the steps of providing a glass blank with low coefficient of expansion, machining a convex shape (4) in the glass blank, laying a front skin (6) impregnated with resin over the convex shape (4) of the glass blank (2), machining in a rear supporting structure (8) a concave shape matching the convex shape machined in the glass blank (2), gluing the concave shape (10) of the supporting structure (8) onto the convex shape of the glass blank (2), machining a convex shape in the supporting structure, laying a rear skin (14) impregnated with resin on a mold, gluing the rear skin (14) onto the convex shape of the supporting structure (8), turning over the assembly so that the blank (2) lies in the upper portion of the assembly, machining and polishing a mirror in the glass blank (2).