A flexible channel to be incorporated into an endoscopic insertion portion having a flexible portion at least in part of its length, for the purpose of providing a flexible passage internally of the endoscopic insertion portion. The flexible channel is composed of a flexible tube with a helical groove on and around its outer periphery, and a reinforcing coil fitted in the helical groove on the flexible tube. At the root of the helical groove, angular projections are formed at intervals in the longitudinal direction and the reinforcing coil is tightly pressed tightly against the angular projections.