As a roller for guiding a coated optical fiber (200), there is used a torsion applying roller (220) having two axes of rotation (C1 and C2). The torsion applying roller (220) guides the optical fiber (200) by its rotation on the first rotation axis (C1) and applies a torsion to the optical fiber by its rotation on the second rotation axis (C2) along a circular locus shown by a dotted line (L2). The coated optical fiber (200) is wound by one turn on the torsion applying roller (220) along a V-groove (221) in the drawing. As a result, the rolling of the coated optical fiber (200) relative to the roller surface of the torsion applying roller (220) is suppressed, so that the torsion is efficiently applied to the optical fiber to reduce the polarization dispersion in the optical fiber sufficiently.