1. An endoscope system comprising: an image pickup section, provided in an endoscope, which performs image pickup; a determining section that determines whether or not a specific observation object exists inside an image pickup region of the image pickup section; a recognizing section that determines whether or not the specific observation object can be recognized as an image from the picked-up image in the image pickup region picked up by the image pickup section; a low visibility determination output section that determines, when the determining section determines that the specific observation object exists inside the image pickup region and the recognizing section cannot recognize the specific observation object as an image, that the image pickup section is in a low visibility condition and outputs a low visibility determination result; and an obstacle estimation section that estimates an obstacle or a type of obstacle which causes the low visibility according to the low visibility determination result.