PROBLEM TO BE SOLVED: To provide an endoscope system capable of treating a paranasal cavity while performing direct observation.SOLUTION: An endoscope system includes: an endoscope that has a distal end part 20 equipped with an optical element for collecting light from a predetermined visual field region and a main body part 21 extending from the proximal end side of the distal end part 20 in the longitudinal direction of the distal end part 20 and having a cross sectional area smaller than the cross sectional area of the distal end part 20 on a surface orthogonal to the longitudinal direction of the distal end part 20, and that captures the image of an inside of a subject； and a guide sheath 32 where an inner channel 321 for movably storing the endoscope is formed and the cross sectional area of the inner channel 321 is equal to or more than the cross sectional area of the distal end part 20, and that guides the endoscope to the paranasal cavity of the subject.SELECTED DRAWING: Figure 4A【課題】副鼻腔を直接観察しながら処置することができる内視鏡システムを提供する。【解決手段】所定の視野領域から光を集光する光学素子を有する先端部２０と、先端部２０の基端側から先端部２０の長手方向に延び、この先端部２０の長手方向と直交する面において先端部２０の断面積より小さい断面積を有する本体部２１と、を有し、被検体の体内画像を撮像する内視鏡と、内視鏡を移動可能に収容する内部チャンネル３２１が形成され、内部チャンネル３２１の断面積が先端部２０の断面積以上であり、内視鏡を被検体の副鼻腔にガイドするガイドシース３２と、を備える。【選択図】図４Ａ
