An endoscope system includes an image forming section configured to arrange first and second images obtained by picking up images of first and second regions of a subject to be adjacent to each other to form an image of one frame, a light source section configured to emit illumination light based on a brightness evaluation of the image to the first and second regions, a brightness-range calculating section configured to detect minimum and maximum luminance values in the first and second images, and an image processing section configured to perform a luminance shift such that a minimum or maximum luminance value of an image, a luminance range of which is smaller than a predetermined luminance range, among the first and second images coincides with a predetermined luminance lower limit or upper limit value.