To shorten the working time of the Fresnel lens and the manufacture time of the metal mold for Fresnel lens molding, and to lower the price of the product by forming a lens group of one continuous spiral groove.

Of the Fresnel lens 10, the lens groove with a V-shaped cross section which consists of a Fresnel surface and a rise surface is formed of the one continuous spiral groove. The rise surface formed of one groove flank of the spiral groove 12 is a slanting surface having the same tilt angle from the spiral outside end 14 to a spiral center end 16. The Fresnel surface of the other groove flank of the spiral groove 12 is varied continuously in tilt angle (Fresnel lens angle) toward a horizontal surface from the spiral outside end 14 to the spiral center end 16. Consequently, the need for a shift to a next lens groove position by moving up and down a cutting tool by lens grooves is eliminated.