PURPOSE: To form a propensity for folding according to a crease by pushing the crease of a band like material into an annular groove of a guide roller by a method wherein a peripheral fringe of a disk is brought into pressure contact onto the crease of the band like material which advances by being hung on a guide roller wherein on the periphery an annular groove is formed, toward the annular groove under the crease of the band like material.

CONSTITUTION: For a band like material 1 which advances by being hung on a guide roller 8, since a crossward positional shift on a flange 8 is prevented, a crease 2 certainly coincides with an annular groove 10 of the guide roller 8. Then, since a peripheral fringe 12 of a disk 11 is brought into pressure contact onto the crease 2 of the band like material 1 on the guide roller 8 toward an annular groove 10 under the crease 2, the crease 2 of the band like material 1 is pushed into the annular groove 10 with the peripheral fringe 12 and bent. Therefore, the crease 2 is made to form a propensity for folding.