An illumination system includes a light source capable of emitting biorhythm control light, a controller that controls a lighting state of the light source, and a manipulation apparatus. The controller executes an introduction mode in which the illuminance of the biorhythm control light is set by gradually increasing or decreasing illuminance of the light source over time, and a stationary mode in which the illuminance of the light source is constantly maintained at the illuminance of the biorhythm control light.