An insertion portion includes a distal end portion (5) including a holding member (15) that holds an observation portion (14), and a bending portion (6) that has a tubular structure. A small-diameter portion (15b) of the holding member (15) is fitted into an inside surface of a distal end side portion of the bending portion (6). A hole (8c) is provided in the distal end side portion of the bending portion (6). A concave portion (15c) is provided at a position in the small-diameter portion (15b) that corresponds to the hole (8c). A screw member (17) in which a screw thread (17a) is formed penetrates the hole (8c) by screw-fastening, and a distal end side thereof is housed in the concave portion (15c). A diameter (φD) in a plane perpendicular to the depth direction of the concave portion (15c) is larger than an outside diameter (φd1) of the screw thread (17a).
