An elastic metal strip aligning a longitudinal direction with a rolling direction of a cold-rolled plate is collected and processed to a shape including a correction plate with the longitudinal direction of the elastic metal as a width direction of a nail and a plurality of tongue strips protruded from the edge of the correction plate near the nail tip. Each tongue strip is folded and bent to form a hooked claw with a double structure of a folding part and a bending part. A nail tip of a deformed nail is inserted between the hooked claw and the correction plate to apply a restoring force of elasticity in the correction plate to the deformed nail as correction ability for deformed nails. A wrought wire rod can be used instead of a cold-rolled plate and a Cu—Al—Mn type shape-memory alloy may further be used as a raw material.
