Provided are an endoscope system, operation method for same, and processor device such that degrees of oxygen saturation are accurately shown by color without being affected by factors such as the distance between the leading end of an endoscope and a subject and the shape of the subject. A light source device (13) of the electronic endoscope system (10) has a white light source (30), a semiconductor light source unit (31), and a rotary filter (34). The white light source (30) constantly emits white light (BB). Blue narrow band light (Nb) from the semiconductor light source unit (31) and green light color separated by the rotary filter (34) are alternately emitted inside the subject. A reflection image of the blue narrow band light (Nb) and a reflection image of the green-colored light are alternately captured. The image data (Nb) obtained when capturing the reflection image of the blue narrow band light (Nb) is normalized with the image data (G) obtained when capturing the reflection image of the green-colored light, and a signal ratio (Nb/G) is obtained. A first oxygen saturation image in which the degrees of oxygen saturation in bloodstream hemoglobin are visually represented is created on the basis of a color table (65a) in which signal ratios (Nb/G) and color information are associated and the abovementioned signal ratio (Nb/G).La présente invention concerne un système dendoscope, un procédé de fonctionnement associé, et un dispositif de processeur permettant de présenter de manière fiable et par couleur les degrés de saturation en oxygène sans linfluence de facteurs tels que la distance entre lextrémité avant dun endoscope et un sujet et la forme du sujet. Un dispositif source de lumière (13) du système dendoscope électrique (10) a une source de lumière blanche (30), une unité source de lumière à semi-conducteur (31), et un filtre rotatif (34). La source de lumière blanche (30) émet une lumière blanche (BB) en continu. La lumière bleue à bande étroite (Nb) de
