1. An endoscope system, comprising: an image signal acquisition unit for acquiring an image signal by imaging a subject; a normal light image generation unit that generates a normal light image, in which a wavelength component of a visible light region is included, based on the image signal; an irregularity image generation unit that generates an irregularity image by extracting only information of irregularities on the subject from the image signal; a first composite image generation unit that generates a first composite image by combining the normal light image with the irregularity image; a blood vessel extraction image generation unit that generates a blood vessel extraction image by extracting a blood vessel located at a specific depth in the subject based on the image signal; a second composite image generation unit that generates a second composite image by combining the normal light image, the blood vessel extraction image, and the irregularity image; wherein the image signal is configured to include image signals of a plurality of colors including at least a blue signal, which has a blue light component having a degree of penetration to a surface layer of body tissue of the subject, and a green signal, which has a green light component having a degree of penetration to a medium-deep layer of the body tissue, and the blood vessel extraction image generation unit extracts the blood vessel at the specific depth based on a ratio of the blue signal and the green signal of the image signals of the plurality of colors.