To obtain the shrink-resistant strong silk two fold single yarn which is not swollen, even when not subjected to a conventional shrink-resistant processing for the surface of the yarn, maintains the properties of a conventional silk two fold single yarn using a strongly twisted yarn, and further maintains the strong properties of decorated strongly twisted yarns, the shrink-resistant effect of the yarn itself and the same touch as that of a conventional crape strongly twisted yarn.

This new shrink-resistant strong silk two fold single yarn 1 is formed by dividing a conventional silk strongly twisted yarn, processing the divided yarns into further twisted strongly twisted yarns 2a, twist-reduced shaft yarns 3a, and so on, and then entwining the yarns around non-shrinkable strong non-twisted yarns 4a or the like in a wrapping state. The decorated strongly twisted yarns 2a, the shaft yarns 3a, and so on, are entwined in such the wholly moderately spiral state as slightly integrally following about the surface of the yarn.