The invention discloses an automatic feeding device for a knitter. The automatic feeding device comprises the knitter, a tractor and an automatic feeding device body, wherein the automatic feeding device body comprises a base, a charging conduit, an adjustment bracket, a falling steel core detection sensor, an incomplete filling detection sensor, a belt pulley, a support, a falling motor, a rubberized steel core, a first annular steel core measurement sensor, a steel core falling detection sensor, a cylinder front position magnetic switch, a buffer cylinder, a knitting point magnetic switch, a feeding cylinder, a cylinder rear position magnetic switch, a slider and a guide rail. Automatic feeding of the steel core in the knitting process can be realized; when the phenomena that the steel core does not fall, two steel cores fall together, the steel core is not on a feeding rack, and the knitter is in an empty knitting state are discovered, the knitter is stopped immediately, an alarm is given and automatic production is realized.