A slit yarn wherein both side parts of the slit yarn are folded one or more times, and the folded width is substantially uniform along the direction of length of the yarn. In this slit yarn, when the width is measured at 20 or more points at intervals of 0.5 m, and the fluctuation coefficient X shown in the following Equation (1) is calculated on the basis of the average value W(avg) and the standard deviation W(.sigma.), this X is (for example) approximately 4% or less. Furthermore, in the slit yarn of the present invention, the abovementioned folded parts are ordinarily shape-set. X(%)=W(.sigma.)/W(avg).times.100 (1)