Endoscopic surgery is a difficult procedure compared with laparotomy surgery. In particular, considerable skills and care are required for thread knotting in endoscopic surgery. In this paper, a method for the automatic identification of a surgical procedure and recognition of a singularity, defined as any unusual manipulation, in the identified surgical procedure is proposed to avoid surgical operation errors. Ligation is divided into several individual procedures, and on the basis of the threshold criteria, each surgical procedure is identified. Next, the identified surgical procedure, thread knotting, is classified as either normal or singular using a self-organizing map (SOM). Experiments were carried out to evaluate the proposed method. The results showed the effectiveness of the proposed method.