To prevent the breakage at a high bending part by executing a shape memorial treatment to a shape memory alloy material, partially executing a solution treatment to a prescribed portion and deformed-working to a prescribed portion and again executing the shape memorial treatment in a state of holding a target shape.

A wire rod (coiled wire rod) 16A of the shape memory alloy, is obtd. by hot-rolling. The solution treatment is executed to remove the working history. A cold-rolling is executed and the shape memorial treatment to the wire rod (coiled wire rod) 16 is linearly executed. The solution treatment to the prescribed portion of the wire rod (coiled wire rod) 16 is executed to make the solution treated portion 20. The wire rod (coiled wire rod) 16 is cut off into a prescribed dimension to obtain a cut-off piece 16A. Bending deformation at 180° to the cut-off piece 16B is executed at the solution treated portion 20 to obtain the worked product 10A. The worked product 10A is restricted to a hairpin shape by using a restricting plates 22 and the shape memorial treatment is executed to obtain the hairpin 10 as the product.