An endotracheal tube according to the present invention is used by being installed into a patient so as to use it together with a device having an insertion section which is inserted into the body. A portion overlapping with the device inserted into the patient is formed as a flat shape； and furthermore, an outer face portion formed along a longitudinal direction of a cross-section, of the portion formed in the flat shape contacts the device.根據本發明之一氣管內管係藉由被裝設至一患者內使其連同一具有一被插入體部內的插入段之裝置使用以供使用。一重疊於插入患者內的裝置之部分係形成為一扁平形狀；尚且，沿著以扁平形狀形成的部分之一橫剖面的一縱向方向形成之一外面部分係接觸該裝置。
