Workpiece processing method and processing device

A workpiece processing method comprising:

• a first forming step of performing forming to impart a predetermined cross-sectional shape to a flat plate-shaped workpiece and obtaining a long workpiece;
• a solution heat treatment step of performing solution heat treatment on the long workpiece after the first forming step has been performed;
• a second forming step of performing forming to bend the long workpiece into an arcuate shape such that a longitudinal direction of the long workpiece describes an arc on the long workpiece after the solution heat treatment step has been performed;
• and
• a third forming step of performing, on the long workpiece after the second forming step has been performed, forming to impart a curved shape to the long workpiece by bringing the long workpiece into contact with a curved surface of a die, and pulling the long workpiece by gripping both ends of the long workpiece, thereby inputting a tensile load in a tangential direction to the curved surface of the die to the long workpiece.