1. An endoscope system comprising: an illumination device for projecting illumination light toward a subject; an image capturing device for capturing an image of light reflected from said subject; an image processing device for generating a blood vessel emphasized/de-emphasized image, in which either first-layer blood vessels located at a predetermined depth or second-layer blood vessels located at a depth deeper than said first-layer blood vessels, or both of them are emphasized or de-emphasized, based on an imaging signal obtained by the image capturing; and a displaying device for displaying said blood vessel emphasized/de-emphasized image.