PROBLEM TO BE SOLVED: To provide a new seam fray stopping method, effectively preventing the occurrence of fray peculiar to a seam of a multi-thread chain stitch, and hardly influenced by applied tension of a needle thread, and provide a seam fray stopping device used in implementing the seam fray stopping method.SOLUTION: A thread guard hook 3 disposed at the back of needle locations A, A is arranged, the thread guard hook 3 is rocked to make a hook part 3b at the tip approach to the back of a looper 1, and among a plurality of thread needle loops captured by the looper 1 at the leading end, a needle thread loop located at the leading side is held. In this state, sewing operation for at least one stitch is performed to pass a descending needle through the held needle thread loop, and the needle thread loop is looped with its own thread by the needle thread held by the needle. The looper thread is pressed by the own thread looping part to prevent slipping-off of the looper thread.