Abstract: In an insertion section of an endoscope according to the present invention, a plurality of flexible segment tubes, each having a predetermined length and a predetermined inside diameter, constitute necessary ducts for the endoscope, individually. The ducts include an image guide duct, light guide duct, instrument channel duct, and air/water channel duct. The flexible segment tubes are fixed in a housing tube. In manufacturing the insertion section, optical fibers and the like are inserted into the flexible tubes, fixed in the housing tube. Once the housing tube is molded, the respective sectional configurations of the flexible tubes are kept uniform, even though the housing tube may contract. Thus, the optical fibers and other elements can be inserted easily into the ducts.