In an endoscope system, a light guide for conducting illumination light from a light source to an endoscope distal end consists of a first fiber bundle and a second fiber bundle. Optical fibers of the first fiber bundle have a smaller numerical aperture than optical fibers of the second fiber bundle. A light volume control mechanism is controlled to project the illumination light only from the first fiber bundle in a close-up inspection mode. In an ordinary inspection mode, the illumination light is projected only from the second fiber bundle. When the volume of light projected from the second fiber bundle toward a target site is insufficient in the ordinary inspection mode, the light volume control mechanism is controlled to let the illumination light be projected from the first fiber bundle.
