An elastic metal strip 10 aligning the longitudinal direction with the rolling direction of a cold-rolled plate is collected and processed to a shape comprising a correction plate 16 with the longitudinal direction of the elastic metal 10 as the width direction of nail and a plurality of tongue strips 11 protruded from the edge of the correction plate 16 near the nail tip. The tongue strip 11 is folded and bent to form a hooked claw 17 with a double structure of a folding part 18 and a bending part 19. A nail tip 21 of a deformed nail 20 is inserted between the hooked claw 17 and the correction plate 16 to apply a restoring force of elasticity in the correction plate to the deformed nail 20 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.
