To provide a yarn feeder having resolved problems that, conventionally, a driven roller, one of yarn feed rollers, is axially supported in a reversibly rotatable manner, therefore if a yarn nipped by both driven and live rollers is subjected to a resistance reversely to the direction of yarn feed, the driven roller is rotated reversely to the direction of yarn feed due to the above resistance, resulting in letting a clamped yarn escape; furthermore, because the respective outer circumferential surfaces of both the driven and live rollers represent metallic surfaces, the coefficient of friction is low, thus representing a factor of letting a clamped yarn escape.

This yarn feeder 70 is such as to be mounted with both a live roller 7b and a driven roller 7c for clamping a yarn and designed to feed a clamped yarn through moving both the rollers; wherein the driven roller 7c to be used is an one-way roller rotatable unidirectionally alone, its outer circumferential surface is made rubbery, and the driven roller 7c is also designed to be contactable with/get apart from the live roller 7b.