To prevent winding of yarn round a yarn roller by inversely taking operation in a yarn delivery process for replacing a yarn package of a fully winding state with an empty bobbin in a yarn winder.

At ordinary yarn winding time, the yarn Y is contacted with a mirror surface area 20s of the yarn roller 20 to make the yarn stably travel. When performing the yarn delivery process, a motor 12 is moved, and a contact area of the yarn Y is changed to a roughened surface area 20r. Thus, since contact frictional force of the yarn Y and the yarn roller 20 reduces, the yarn Y easily slides on a surface of the yarn roller 20, so that even if tensile force of the yarn Y on the downstream side of the yarn roller 20 reduces when performing the inversely taking operation for reversing the rotational direction of the empty bobbin 9 and the traveling direction of the yarn Y, the yarn Y can slide on the surface of the yarn roller 20 so as to eliminate unbalance of the tensile force of the yarn Y between the upstream side and the downstream side of the yarn roller 20 to prevent winding of the yarn Y round the yarn roller 20 by deflection of the yarn Y.