An illumination system includes: a light-emitting module including a blue LED light source that emits blue light having a light emission peak in a blue range of from 400 nm to 470 nm and a red LED light source that emits red light having a light emission peak in a red range of from 610 nm to 680 nm; a light regulator that controls a first light intensity, which is light intensity at the light emission peak in the blue range, and a second light intensity, which is light intensity at the light emission peak in the red range, in a light emission spectrum of light emitted by the light-emitting module; and a clock that measures a time. The light regulator causes the second light intensity to change in conjunction with a change in the first light intensity, in accordance with the time measured by the clock.