1. An endoscope system, comprising: a suturing member for suturing between parts of an organ separated by predetermined surgery; an imaging unit for imaging a sutured portion that is sutured by using the suturing member; an oxygen saturation image generation section for generating an oxygen saturation image by imaging an oxygen saturation of the sutured portion based on image information obtained by the imaging unit; a determination section that detects an area of a low oxygen region which is within a predetermined range of oxygen saturation in the oxygen saturation image and determines a suture state of the sutured portion based on the area of the low oxygen region; and a display device for displaying the oxygen saturation image and a result of the suture state of the sutured portion which is determined by the determination section.