The endoscope according to the present invention includes an insertion portion 2 to be inserted into a subject, an operation portion 3 provided continuously to the proximal end side of the insertion portion, and an insertion portion provided in or inside the insertion portion. A hard partition wall 21 that maintains water tightness between the first space S1 including the interior and the second space S2 formed on the base end side of the first space, and the partition wall provided in the partition wall from the first space to the second space. And a first check valve 22 that circulates the gas and prevents the gas from flowing from the second space to the first space.本発明の内視鏡は、被検体に挿入される挿入部２と、挿入部の基端側に連設される操作部３と、挿入部の内部又は操作部の内部に設けられ挿入部の内部を含む第１空間Ｓ１と第１空間の基端側に形成される第２空間Ｓ２との間の水密性を維持する硬性の隔壁２１と、隔壁に設けられ第１空間から第２空間へと気体を流通させ第２空間から第１空間への気体の流通を阻止する第１逆止弁２２とを具備する。
