An endoscope system includes: an image pickup apparatus in which an insertion portion including an objective optical system is detachable, the image pickup apparatus being configured to pick up an optical image of light from an observed object transmitted by the objective optical system of the insertion portion and to output the optical image as an image pickup signal a focus changing section provided in the image pickup apparatus and including a drive section that can change focus of the image pickup apparatus a control section configured to generate a control signal for automatically controlling the optical image in a focused state for the drive section of the focus changing section in a state in which the insertion portion is fitted to the image pickup apparatus and an optical characteristic acquiring section configured to acquire an optical characteristic of the insertion portion used by the control section to generate the control signal.
