PURPOSE: To work the toric surface in high efficiency and with high accuracy by allowing the article to be ground to rotate on the circumference of a generatrix radius and to revolve in the perpendicular direction to the above with a radius of turn equivalent to the sub-generatrix radius, and grinding the article by the grindstone equipped with the concave surface having the sub-generatrix radius.

CONSTITUTION: The lens 2 whose toric surface is to be worked is installed on a cylindrical jig 1 so that the distance from the rotary shaft A is the generatrix radius R1 of the toric surface. The cylindrical jig 1 is set slidably on a rotating base 5, so the jig 1 can be turned around the rotary shaft C which is perpendicular to the rotary shaft A and departed from said shaft A by the difference R1-R2 between the generatrix line radius R1 and the sub-generatrix radius R2. The cylindrical jig 1 is revolved and turned around the rotation shaft A and the revolution shaft C, and the lens 2 is worked by the rotaty grindstone 3 having the concaved surface of the sub-generatrix radius R2. Thus, the toric surface having the generatrix radius R1 and the sub-generatrix radius R2 can be worked on the lens.