An electronic endoscope system includes: an electronic endoscope including an image sensor that images a living tissue; a processor that performs image processing on an image obtained by imaging the living tissue; and a display that displays the image on which image processing has been performed. The processor includes: a feature amount calculation unit that calculates, as a feature amount, a ratio between differences of values of two color signals out of a plurality of color signals of each of pixels of the image from a reference value; and an image enhancement processing unit that enhances the image by determining a degree of increase or decrease of at least one of the values of the two color signals on the basis of the calculated ratio so as to perform enhancement processing on the image.