A guide sheath which extends along a longitudinal axis, which is configured to be guided by an internal introduction device and be inserted into a body, and which has a channel through which a medical device is capable of being inserted so as to guide a distal end of the medical device to a target area, the guide sheath comprising: a bending section being provided at a distal end of the guide sheath; a first conduit line formed on the longitudinal axis and forming the channel; a pair of second conduit lines (120b, 120c) formed and disposed radially outside the first conduit line, wherein said conduit lines (120a, 120b, 120c) extend in a longitudinal direction of the guide sheath being formed at the bent section; a pair of manipulation wires (126, 127), one manipulation wire (126, 127) being disposed in one of the second conduit lines (120b, 120c), respectively, and extending along the longitudinal axis so as to be capable of advancing and retracting; and characterized by further comprising the bent section formed of a thermoplastic resin, the bent section being configured to be bent in accordance with advance or retraction of the manipulation wires (126, 127), wherein the bent section includes partition walls formed at positions which are radially outside both the first conduit line and the second conduit lines (120b, 120c) and which are between an outer surface of the bent section and the second conduit lines (120b, 120c), wherein the bent section is configured such that a plurality of hard sections are alternately disposed on a soft section along the longitudinal axis, wherein the soft section has a predetermined bending stiffness and hard sections have bending stiffness larger than the soft sections formed by cross-linking the thermoplastic resin by radiating ionizing radiation to the thermoplastic resin, wherein each hard section is formed in a plate shape, which is a substantially semi-circular shape when seen in the longitudinal direction in parallel and distal end sections of the manipulation wires (126, 127) are fixed to the most distal hard sections. a bending section being provided at a distal end of the guide sheath; a first conduit line formed on the longitudinal axis and forming the channel; a pair of second conduit lines (120b, 120c) formed and disposed radially outside the first conduit line, wherein said conduit lines (120a, 120b, 120c) extend in a longitudinal direction of the guide sheath being formed at the bent section; a pair of manipulation wires (126, 127), one manipulation wire (126, 127) being disposed in one of the second conduit lines (120b, 120c), respectively, and extending along the longitudinal axis so as to be capable of advancing and retracting; and characterized by further comprising the bent section formed of a thermoplastic resin, the bent section being configured to be bent in accordance with advance or retraction of the manipulation wires (126, 127), wherein the bent section includes partition walls formed at positions which are radially outside both the first conduit line and the second conduit lines (120b, 120c) and which are between an outer surface of the bent section and the second conduit lines (120b, 120c), wherein the bent section is configured such that a plurality of hard sections are alternately disposed on a soft section along the longitudinal axis, wherein the soft section has a predetermined bending stiffness and hard sections have bending stiffness larger than the soft sections formed by cross-linking the thermoplastic resin by radiating ionizing radiation to the thermoplastic resin, wherein each hard section is formed in a plate shape, which is a substantially semi-circular shape when seen in the longitudinal direction in parallel and distal end sections of the manipulation wires (126, 127) are fixed to the most distal hard sections.