An endoscope system includes an endoscope including an image pickup section that picks up an image of a subject lumen organ, a recording section that records three-dimensional image information of a lumen organ acquired from a medical diagnosis apparatus, a position estimating section that estimates a distal end position of the endoscope, a lumen-diameter acquiring section that acquires a lumen diameter of the organ in the estimated position of the distal end, a condition determining section that determines whether the acquired lumen diameter is smaller than the reference lumen diameter, an image-change-amount detecting section that detects a change amount of a predetermined parameter in an endoscopic image picked up by the image pickup section, a virtual-endoscopic-image generating section that generates a virtual endoscopic image from any visual point position, and an information recording section that records a position of a distal end of an insertion section and the virtual endoscopic image.
