To provide an apparatus and a method for knitting fabric using elastic yarns, in which the elastic yarns are able to be used while correcting the difference between the set tension and the actual tension without being subject to a lowered knitting efficiency or restrictions to knitting patterns.In a knitting machine 1, a tension meter 7 detects the actual tension T2 of a rubber yarn 5 when a carriage 3 reverses the running direction outside the knitting width of a fabric 9. The yarn sending length F at which the rubber yarn 5 is sent out from a yarn sending device 8 to a yarn route pathway for each knitting course is able to be obtained in advance as the length of the rubber yarn 5 consumed under the designated tension T1 for each knitting course. The yarn sending length F is corrected in such a manner that the difference between natural lengths L1, L2 of the rubber yarn 5, existing in the yarn route pathway under the set tension T1 and the actual tension T2, decreases.