To provide a shape correcting method for a concave forming tool capable of easily providing a desired tool shape and efficiently conducting the correcting work of the tool shape.

A grinding wheel 3 having a concave machining face matched with the machining shape of a convex lens is used, the lens held by a holder 2 is pressed to the grinding wheel 3 being rotated, and the grinding wheel 3 or the lens is rocked with the curvature center of a lens machining face serving as the rocking center to machine the lens by this shape correcting method for the concave grinding wheel 3 in this lens machining device. A shape correcting tool 20 having a plane is removably fitted to the holder 2, and the shaft center of the holder 2 and the shaft center of the grinding wheel 3 are coaxially located. The grinding wheel 3 is rotated for machining while the plane of the correcting tool 20 is pressed to the end face of the grinding wheel 3 together with the holder 2, and the correcting tool 20 is removed after the end face of the grinding wheel 3 is machined to the desired position.