To suppress a tension fluctuation with a dancer roller by setting the diameters of grooves at the center section wound with a wire to form a cutting section within many grooves formed on the peripheral face of a grooved roller larger than the diameters of grooves at end sections.

A wire traveled at a high speed at a cutting section is applied with the tension required for cutting in a grooved roller 44. When the wire is shifted from the grooves 48 of the grooved roller 44 to grooves 46, the peripheral speed of the wire is increased as the diameters of the grooves 46 are increased, and it is applied with prescribed tension. When the wire having traveled a cutting section travels at the position of the grooves 48 from the grooves 46, the peripheral speed is lowered as the diameters of the grooves 48 are shrunk, and tension is decreased. Tension is applied to the wire by the grooved roller 44, the tension is decreased in the grooved roller 44, and the tension of the wire is decreased on the outside of the grooved roller 44, thereby the load applied to a wire reel is reduced.