To provide a ring shape blank for roll-forming work, which ring shape blank can reduce a machining allowance in cutting work after performing the roll-forming work to a minimum, and further can form a ring shape product having a high strength by fully causing a flow (plastic flow) of material by the roll-forming work, when an asymmetrical ring shape product having an annular projection at its one end is manufactured by the roll-forming work.

The ring shape blank is formed by the roll-forming work into the asymmetrical ring shape product having the annular projection at its one end, and is composed of a large diameter portion 2 and a small diameter portion 3. The large diameter portion 2 is continuous with the small diameter portion 3 via a tapered portion 4 formed so as to have a definite taper angle α.