To provide a new ravel preventing method and ravel preventing apparatus capable of effectively preventing the occurrence of raveling peculiar to a seam formed by a multi-thread chain stitch without being influenced by applied tension of a needle thread and a looper thread, and to provide a seam structure formed by the method and apparatus.

A thread hook 3 and a looper thread retainer 6 are disposed behind needle locations A and A. The thread hook 3 and the looper thread retainer 6 are rocked to allow a hook part 3b and a thread receiver 6a at their tips, respectively, to approach a looper 1. The hook part 3b retains a needle thread loop caught by the looper 1 and locates the left side needle thread loop at a position which is closer to the advance end of the looper 1 than is the needle location A. The thread receiver 6a locates a looper thread extending from the looper 1 to a fabric to be sewn in front of the needle location A. Then, a sewing operation is performed for at least one stitch.