PURPOSE: To prevent generation of crack by melting through argon inner gas arc the part where stress concentration is generated at the time of press forming and then forming a solidified molten part.

CONSTITUTION: A metal plate is blanked in a prescribed shape by blanking, and a blanked plate is formed. The part where stress concentration is generated in the blanked plate 1 at the time of press forming is melted by the arc discharge 8 generated from the tip end of a tungsten electrode 7 and by the inner gas arc of the surrounding inner gas reservoir 9, and then solidified to form the molten part 10 on an end face 2. The molten part 10 is composed of curved surface without edge. Because of the existence of the molten part 10, crack is not generated when bending is performed.