A mantle tube (3; 203), comprising: a bendable member that is formed in such a way as to be received in an elongate, annular, cylindrical member and includes two fixed sites (11, 15) that are fixed to the cylindrical member and a bendable site that is interposed between the fixed sites (11, 15) and bendable in a direction intersecting a longitudinal direction thereof, so that the cylindrical member is bent following the bendable site in the direction intersecting a longitudinal direction thereof, and an angle adjustment member that is capable of adjusting a bending angle of the bendable site, characterized in that the mantle tube (3; 203) further comprises: a plurality of interconnected structure-forming members that are separated from the two fixed sites (11, 15) and the bendable site and extend along the bendable site for interconnection to a wire member along a longitudinal direction of the interior of the cylindrical member, whereby the plurality of interconnected structure-forming members are arranged along the wire member and capable of coming into contact with one another and spacing away from one another in an arrangement direction thereof, and an angle holding mechanism that is capable of holding the bendable site bent by the angle adjustment member by the interconnected structure-forming members at any desired bending angle. a bendable member that is formed in such a way as to be received in an elongate, annular, cylindrical member and includes two fixed sites (11, 15) that are fixed to the cylindrical member and a bendable site that is interposed between the fixed sites (11, 15) and bendable in a direction intersecting a longitudinal direction thereof, so that the cylindrical member is bent following the bendable site in the direction intersecting a longitudinal direction thereof, and an angle adjustment member that is capable of adjusting a bending angle of the bendable site, characterized in that the mantle tube (3; 203) further comprises: a plurality of interconnected structure-forming members that are separated from the two fixed sites (11, 15) and the bendable site and extend along the bendable site for interconnection to a wire member along a longitudinal direction of the interior of the cylindrical member, whereby the plurality of interconnected structure-forming members are arranged along the wire member and capable of coming into contact with one another and spacing away from one another in an arrangement direction thereof, and an angle holding mechanism that is capable of holding the bendable site bent by the angle adjustment member by the interconnected structure-forming members at any desired bending angle. a plurality of interconnected structure-forming members that are separated from the two fixed sites (11, 15) and the bendable site and extend along the bendable site for interconnection to a wire member along a longitudinal direction of the interior of the cylindrical member, whereby the plurality of interconnected structure-forming members are arranged along the wire member and capable of coming into contact with one another and spacing away from one another in an arrangement direction thereof, and an angle holding mechanism that is capable of holding the bendable site bent by the angle adjustment member by the interconnected structure-forming members at any desired bending angle.