PROBLEM TO BE SOLVED: To provide an insertion device that can efficiently suck and remove only a gas in a subject in a configuration having multiple conduit lines in an insertion part.SOLUTION: The insertion device includes: the insertion part 4； the multiple conduit lines 10u, 10r, 10l, 10d respectively having opening 10us, 10rs, 10ls, 10ds； a sensor part 15 for detecting a region R where liquid in a subject is accumulated； and a control part 60 for blocking or stopping suction via the conduit lines 10u, 10r, 10l, 10d where the openings 10us, 10rs, 10ls, 10ds are positioned in the region R where the liquid in the subject is accumulated, in the multiple conduit lines 10u, 10r, 10l, 10d, based on a detection result of the sensor part 15.SELECTED DRAWING: Figure 2
