PROBLEM TO BE SOLVED: To provide a medical system improving an introduction property and recovering property, into and from the body, of a medical instrument used retained in a body internal wall.SOLUTION: This medical system 1 includes: a medical instrument 2 that includes a capsule-like outer sheath 10 having an observation window 10a and incorporating an imaging means and that is retained in the body wall 102 in the body 101 and a body wall contact means 14 that is adapted to be linearly moved along the longitudinal direction of the outer sheath 10 and to be engaged with the end portion 11 of the outer sheath 10, when the medical instrument 2 is introduced into the body 101, and that is adapted to be moved to a position of the outer sheath 10 outside a region of the observation window 10a, come into contact with the body wall 102 and secure a space between the outer sheath 10 and the body wall 102, when the medical instrument 2 is retained in the body wall 102.
