The purpose of the present invention is to dispose a medical device at a suitable position in accordance with the curved shape of an over-tube. A medical system (1) relating to the present invention is provided with: a long and flexible medical device (2)； a long and flexible over-tube (4) having a channel (3), into which the medical device is to be inserted in the longitudinal direction； and a system main body (5) having a base section that fixes the base end of the over-tube, a moving mechanism (16), which is provided to the base section, and on which the base end of the medical device is removably mounted, said moving mechanism moving the medical device in the longitudinal direction with respect to the over-tube, and a control unit (17) that controls the moving mechanism. The over-tube is provided with: a wire (13), which is fixed to the leading end of the over-tube, and which extends in parallel to the channel, said wire being supported such that the wire can relatively move merely in the longitudinal direction； and a sensor (14) that detects the protruding length of the wire from the base end of the over-tube. On the basis of the protruding length of the wire, said protruding length having been detected by means of the sensor, the control unit calculates a channel path length.Le but de la présente invention est de disposer un dispositif médical au niveau d'une position appropriée en accord avec la forme incurvée d'un surtube. Un système médical (1) selon la présente invention comprend : un dispositif médical long et flexible (2) ； un surtube long et flexible (4) comportant un canal (3) dans lequel le dispositif médical doit être inséré dans la direction longitudinale ； et un corps principal de système (5) comportant une section de base qui permet de fixer l'extrémité de base du surtube, un mécanisme de déplacement (16), qui est disposé sur la section de base, et sur lequel l'extrémité de base du dispositif médical est montée de manière amovible, ledit mécanisme
