To reduce manufacturing costs and unnecessitate troublesome inventory management of a die by forming a camber without using the die.

A main roll 22 driven to rotate with a first servo motor is arranged in front of a table 19. A pinch roll 27 holding a plate spring stock between the main roll 22 and the pinch roll is arranged so as to vertically move in the position facing the lower side of the main roll 22 in the table 19. An upstream side sub-roll 30 and a downstream side sub-roll 31 are arranged so as to vertically move via ascending and descending mechanisms 32, 33 in the upstream side and the downstream side of the pinch roll 27 held the plate spring stack in the table 19. And both sub-rolls 30, 31 are abutted from the lower side to the plate spring stock held between the main roll 22 and the pinch roll 27 by vertically transferring both sub-rolls 30, 31, whereby, required bending is executed.