1. An endoscope system, comprising: an imaging device that acquires an image signal by imaging a subject; and a processor device performs to, generate a normal light image, in which a wavelength component of a visible light region is included, based on the image signal, generate an irregularity image by extracting only information of irregularities on the subject from the image signal, generate a first composite image by combining the normal light image with the irregularity image, generate a blood vessel extraction image by extracting an image of a blood vessel located at a specific depth in the subject based on the image signal, generate 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 processor device extracts the image of 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.