1. An endoscope system comprising: an insertion section that is inserted into a subject; an objective optical window that is provided on a distal end side of the insertion section and receives light from the subject; an image pickup section that picks up an image inside the subject from the light made incident from the objective optical window; a position-information acquiring section that acquires position information of the objective optical window; a recording section that records an intra-subject image acquired by the image pickup section and the position information acquired by the position-information acquiring section in association with each other; an associating section that associates the position information recorded in the recording section with a model image of a predetermined organ in the subject; an image generating section that generates, as a pasted image, an image obtained by pasting the intra-subject image onto the model image of the predetermined organ associated by the associating section; a determining section that determines whether a predetermined trigger signal concerning the image pickup in the image pickup section is generated or a predetermined feature value of the intra-subject image acquired by the image pickup section satisfies a predetermined condition; and a control section that applies processing for pasting the intra-subject image, concerning which the predetermined trigger signal is determined as being generated or the predetermined feature value of which is determined as satisfying the predetermined condition by the determining section, closer to a front surface than other intra-subject images on the pasted image and applies image processing to the intra-subject image pasted onto the front surface to be distinguishable from the other intra-subject images.