Abstract: A yarn feeding device includes a mounting frame fastened to the frame structure of a circular knitting machine to hold a yarn guide plate, a driving wheel, a yarn guide bracket, a plurality of plastic yarn tension guides, and a plurality of yarn feeding wheels. Each yarn tension guide has a rotating tension adjustment plate stopped at the respective yarn tension guide rod and turned to adjust the oscillating amplitude of the respective yarn tension guide rod so that the degree of circumferential engagement of the respective yarn with the wheel surface of the respective yarn feeding wheel is relatively adjusted.