Provided is a method capable of changing the direction/shape of a converging portion and the degree of convergence arbitrarily. Passages for a plurality of elongated elastic members (13) toward a first nip roll (20) are provided with a rocking unit (30) for rocking in a CD direction, which is equipped with such passages (31) along an MD direction as are spaced in the CD direction and of the same number as that of the elongated elastic members (13). Near the downstream of the passages (31) in the rocking unit (30), there are disposed a plurality of guide members (32) which are so disposed in the CD direction as to move in the CD direction with respect to the passages (31). The plural elongated elastic members (13) are individually threaded through the passages (31) and further through the guide members (32) to the first nip roll (20). While the plural elongated elastic members (13) are being rocked by the rocking unit (30), the clearances between the guide members (32) are narrowed to converge the plural elongated elastic members threaded between the guide members (32).
