Arranging two observation components inside intraperitoneal via natural opening of the organism, the medical behavior which can guarantee two points of view and in order to offer the system, sutra natural open medical behavior, thing and the description above which introduce the 2nd observation device into intraperitoneal from the aforementioned opening which was formed especially and the aforementioned tube cavity organ which introduce the 1st observation device into intraperitoneal from the aforementioned opening which was formed especially and the aforementioned tube cavity organ which form opening in the tube cavity organ making use of the device which from natural opening of the patient is inserted into the tube cavity organ 2ndThe observation device from the aforementioned 1st observation device with the picture which is obtained from thing and the aforementioned 1st equipment observation device which are arranged in another position and while the picture which is obtained from the aforementioned 2nd observation device making indicate in selectively, or making indicate in simultaneously and verifying the picture doing the hand skill of desire inside intraperitoneal, with it includes.2つの観察部材を生体の自然開口を通じて腹腔内に配置して、2つの視点を確保することができる医療行為およびシステムを提供するために、経自然開口的な医療行為が、患者の自然開口から管腔器官内に挿入されたデバイスを用いて管腔器官に開口を形成することと、前記管腔器官に形成した前記開口から第1の観察装置を腹腔に導入することと、前記管腔器官に形成した前記開口から第2の観察装置を腹腔に導入することと、前記第2の観察装置を前記第1の観察装置とは別の位置に配置することと、前記第1の装観察装置から得られる画像と、前記第2の観察装置から得られる画像とを選択的に表示させ、又は同時に表示させることと、画像を確認しながら腹腔内で所望の手技をすること、とを含む。