The invention provides a ripped seam prevention method for a stitch and a sewing machine. According to the method, after general sewing of double lock stitch is finished, a needle and thread loop of a needle positioned on an advancing side of a curved needle is at least caught and retained by the aid of a thread retaining component, the needle drops into the retained needle and thread loop, the needle and thread loop is automatically connected by the aid of the retained needle and thread of the needle, and the tip of the needle projects from the lower surface of a needle plate and drops into the range of the lower surface of the curved needle when the needle and thread loop is caught by the thread retaining component, and the thread retaining component catches the upstream portion of the needle and thread loop caught by the curved needle relative to the curved needle. Skipped stitching and cutoff of the needle and thread loop can be prevented, the needle and thread loop is prevented from being enlarged after seams are ripped, and a driving device is miniaturized.