An object of the invention is to increase quality and aesthetic appearance by eliminating the formation of knots in piecing spun yarn and the mixing of colors and the projection of end yarn. Tip end sides (11a, 12a) of two spun yarns (11, 12) are turned back in the shape of "J", and opposed to each other so that turned-back portions (11b, 12b) can be linked to each other. The tip end sides (11a, 12a) are intertwined to the base end sides (11c, 12c) of the turned-back portions (11b, 12b) so as to be joined to each other. Since, the tip end sides (11a, 12a) of the spun yarns (11, 12) are intertwined to the base end sides (11c, 12c) of the turned-back portions (11b, 12b) so as to be joined to each other, and the intertwining is performed within the spun yarns (11, 12), piecing can be securely performed irrespective of the type of a mating material. Since no knot is formed, the possibility can be lowered that a portion of knitting yarns becomes an obstacle when forming stitches, or is caught on a knitting needle and breaks the yarns. Since the yarns are linked to each other at the turned-back portions (11b, 12b), color mixture is not caused even when the colors of the yarns are different from each other, and thus quality and appearance can be improved.