PROBLEM TO BE SOLVED: To provide a gas supply system and a gas supply device that can realize operability fitting sensation of an operator while preventing intraluminal pressure from rising rapidly.SOLUTION: A manual-gas-supply connector 145 of a gas supply device 66 is connected to an endoscope 10, and when an operator operates a gas-supply/water-supply button of the endoscope 10, carbon dioxide gas is supplied into a gastrointestinal tract of a patient through an internal conduit of the endoscope 10 (manual gas supply). However, an automatic-gas-supply connector 144 of the gar supply device 66 is connected to an insertion aid that guides the endoscope 10 into the gastrointestinal tract, and when automatic gas supply is set to the on state by pressing an automatic-gas-supply button 212 of the gas supply device 66, the carbon dioxide gas is intermittently supplied into the gastrointestinal tract of the patient from the automatic-gas-supply connector 144 through the insertion aid so that pressure in the gastrointestinal tract becomes set pressure (automatic gas supply). In this kind of gas supply system, a gas supply flow rate in the manual gas supply is in a high state when the automatic gas supply is in the off state, and is switched to a low state when the automatic gas supply is in the on state.【課題】管腔内の圧力が急激に高くなることを防止しつつ、術者の感覚に合った操作性を実現することができる送気システム及び送気装置を提供する。【解決手段】送気装置６６の手動送気コネクタ１４５は、内視鏡１０に接続され、術者が内視鏡１０の送気・送水ボタンを操作することにより、内視鏡１０の内部管路を介して患者の消化管内に炭酸ガスが送気される（手動送気）。一方、送気装置６６の自動送気コネクタ１４４は、内視鏡１０を消化管内に案内する挿入補助具に接続され、送気装置６６の自動送気ボタン２１２を押して自動送気をオンに設定すると、消化管内の圧力が設定圧となるように自動送気コネクタ１４４から挿入補助具を介して患者の消化管内に炭酸ガスが間欠的に送気される（自動送気）。このような送気システムにおいて、手動送気の送気流量は自動送気がオフのときには高流量、自動送気がオンのときは低流量に切り替えられる。【選択図】図６
