PURPOSE: To prevent process trouble, such as yarn breakage or single fiber breakage, while holding uniform adhesion performance in the longitudinal direction of a yarn, by excessively feeding an oiling agent to a weighing and oil feeding guide and setting the return amount of the oiling agent from the weighing and oil feeding guide within a specific range.

CONSTITUTION: An oiling agent in an weighed state is excessively discharged from a discharging hole 9 of an oil feeding guide 2. The amount (return amount) of the oiling agent, flowing down, dripped and returned from the lower end of the oil feeding guide 2 without being applied and accompanied by a yarn is 0.1-3.0% based on the supply rate of the oiling agent. Since the excessively fed oiling agent is made to flow down the whole groove width of a yarn contact part 3, a yarn contact part having a groove width (W) somewhat larger than a theoretical yarn width in the yarn contact part is preferably adopted.