PURPOSE: To reduce flaws on a formed part by adjusting the position of a forming roller and giving radius bending and also spiral pitch.

CONSTITUTION: An article 3 to be formed is bent with three or more forming rollers 1, 4, 5. Then, the position of the forming rollers 1, 4, 5 is adjusted and radius bending and also spiral pitch are given. The adjustment of the forming rollers is done by adjusting the height of the forming roller 1 on the outlet side in the axial direction on the basis of the forming roller 5 on the inlet side and the intermediate forming roller 4. The arrangement of the forming rollers is constituted so as to adjust the inclination of the shaft of the forming roller 1 on the outlet side on the basis of the forming roller 5 on the inlet side and the intermediate forming roller 4. In this way, a lifting roller can be omitted and bend shape can be smoothed.