PURPOSE: To manufacture the V-shape spiral bar stock without generating wrinkles by forming the curved part with each roll along the locus of circular arc that the bending diameter in the longitudinal direction is made successively smaller, and curving the band steel passing through these rollers inclining the band steel by the fixed lead angle.

CONSTITUTION: A flat band steel 12 is formed continuously and automatically to a sectional shape of upwarding circular arc like 17, a section of half circular shape 21, a sectional of tulip shape 25 and a section of V shape 35 by step, and at the same time it is curbed while making the bending radius smaller successively in the longitudinal direction. And because it is brought to the side direction with the constant lead angle, the compressive load is not applied to both side walls of the section of V shape, and the stress is not generated. Therefore, the spiral bar stock with section of V shape of good quality without wrinkles on the both side walls of the section of V-shape and with completely nothing of cracks can be manufactured efficiently and at a low cost.