An auxiliary tool for colonoscopy is disclosed. The auxiliary tool for colonoscopy includes an anal intubation body and a feces-holding body. The anal intubation body has an aperture surface on one side and an anus cover on the other side, and also has a hollow part having a first diameter formed inside. The anus cover is shaped as a cap having a round curved surface. The feces-holding body has one side coupled to an inner side of the anus cover, has a holding part formed inside, and has a leakage prevention body formed on the other side. The holding part has a second diameter and is connected with the hollow part, and the leakage prevention body is configured to permit passage of an endoscope tube but prevent leakage of fecal matter held in the holding part to the other side. The auxiliary tool for colonoscopy can prevent damage to the anus during colonoscopy and guarantee a field of vision around the anal verge to allow accurate observation and diagnosis over an area extending from the anal verge to the lower rectum.
