PROBLEM TO BE SOLVED: To provide a medical device capable of preventing unintended leakage of a fluid to the outside while maintaining an observation visual field for performing an operation on an affected part in a body cavity.SOLUTION: A medical device comprises: an insertion part which can be inserted into a body cavity； a first conduit which is provided inside the insertion part and has a first opening communicating with the outside at a distal end side, and whose base end side is connected to a suction device for sucking a fluid from the first opening； a second conduit provided to branch from the middle of the first conduit and comprising a second opening communicating with the outside； a flow path formation member forming a flow path from the second opening to the base end side of the first conduit and capable of taking in outside air around the second opening； and a selector valve for switching a flow path when the suction device sucks the fluid to either a flow path through which the fluid sucked from the first opening is directly circulated to the base end side of the first conduit or a flow path through which the fluid sucked from the second opening is circulated to the base end side of the first conduit via the flow path formation member.SELECTED DRAWING: Figure 1【課題】体腔内の患部に対して手術を行う際の観察視野を維持しつつ、外部への意図しない流体の漏出を防ぐことが可能な医療機器を提供する。【解決手段】医療機器は、体腔内に挿入可能な挿入部と、挿入部の内部に設けられ、外部へ連通する第１の開口を先端側に備え、第１の開口から流体を吸引する吸引装置に基端側が接続されている第１の管路と、第１の管路の途中から分岐して設けられ、外部へ連通する第２の開口を備えた第２の管路と、第２の開口から第１の管路の基端側へ至る流路を形成するとともに、第２の開口の周辺の外気を取り込み可能な流路形成部材と、吸引装置が流体を吸引する際の流路を、第１の開口から吸引した流体を第１の管路の基端側へ直接流通させる流路、または、第２の開口から吸引した流体を流路形成部材を経由して第１の管路の基端側へ流通させる流路のいずれかに切り替える切替弁と、を有する。【選択図】図１
