We experienced a very rare complication of colonoscopy, a migration of stiffening tube into the colorectum. We herein introduce a withdrawing method of migrating stiffening tube incidentally inserted into the colorectum. A 65-year-old Japanese woman underwent colonoscopy because of abdominal discomfort. We used stiffening tube to insert the scope to the proximal colon because of her redundant sigmoid colon. When withdrawing the scope, we realized that the tube was fully inside the colorectum. We could not remove the tube instantly, and it reached the splenic flexure, finally. We reinserted the scope through the migrating tube, straightened the scope, and withdrew it holding a slight angle of the scope over the proximal end of the tube. Then, we could safely remove the tube along with the scope through the anus.