A yarn-feeding device for a circular knitting machine

A yarn-feeding means used in a circular knitting machine for plating knitting im which a ground yarn (18a) acid an elastic yam (16a) are knitted together. The yam feeding means comprise a first yarn-feeding device (15a) that feeds the ground yam (18a), a second yarn-feeding device (15b) that feeds the elastic yarn (16a) and a guide roller (8b) that guides the elastic yam (16a). The yarn feeding means is provided with a disengagement-preventing member (8c; 88c; 8f) that prevents the elastic yarn (16a) from coming off the guide roller (8b) which member is positioned close to the guide roller (8b). The disengagement-preventing member (8c) can be moved according to an angle of advance of the elastic yarn (16a). The disengagement-preventing member (8c) may be a spiral wire mounted on a yarn carrier (8).