Provided is a manipulator (1) including a movable section (3), a driving section (4) that generates power to be supplied to the movable section (3), a long guide member (2) that is elongate and flexible and that has one end to which the movable section (3) is attached and another end to which the driving section (4) is attached, an elongated tensile-force transmitting member (5) that transmits the power of the driving section (4) to the movable section (3) by means of a tensile force, and a tensile-force adjusting mechanism (6) that adjusts the tensile force of the tensile-force transmitting member (5). The long guide member (2) includes an elongate and flexible guide tube (11) having a lumen (10) through which the tensile-force transmitting member (5) longitudinally extends, and also includes an outer sheath (12) having higher rigidity than the guide tube (11). The outer sheath (12) covers an outer periphery of the guide tube (11) and has a proximal end section (13) that is movable relative to the driving section (4) in a longitudinal direction of the guide tube (11). The tensile-force adjusting mechanism (6) adjusts a position of the proximal end section (13) of the outer sheath (12) relative to the driving section (4) in the longitudinal direction of the guide tube (11).
