PURPOSE: To convey a yarn at a high speed and with a low tension while preventing the yarn from vibrating at a separating point and from being wound around a roller or the like, by jetting a fluid to a yarn-delivering part of a yarn-conveying roller in the direction opposite to the moving direction of the yarn.

CONSTITUTION: The yarn Y wound plural times around a pair of rollers 1, 1' is delivered from the right-side roller 1', is introduced to a yarn-treating nozzle 2 provided on the downstream side of the roller and is subjected to a false twisting or a twisting treatment under the action of a fluid fed into the nozzle 2 through a fluid supply pipe 3. In this case, a fluid is jetted from a nozzle 4 to the yarn-separating point 1'a part of the roller 1' in the direction opposite to the moving direction of the yarn, and is caused to flow into the point 1'a part. Accordingly, the yarn Y is stably delivered while preventing it from vibrating and from being wound around the roller 1', under the effect of the viscous friction between the roller 1' and the yarn or the effect of an airflow developed at the periphery of the roller 1'.