A lighting system for preventing a plant disease damage is provided with an ultraviolet light source which emits ultraviolet ray including UV-B in a wavelength region of 255 to 340 nm, a visible light source which emits visible light, and controllers which control a lighting of the ultraviolet light source and the visible light source. The controller controls the lighting of the ultraviolet light source so that a horizontal irradiance on a canopy surface of a plant is 50 μW/cm2 or less during a predetermined daytime period. The controller controls the lighting of the visible light source so that a horizontal illuminance on a canopy surface of a plant is 10 lux or less during a predetermined nighttime period. The lighting system promotes a component change of the plant effectively by a stimulation by the UV-B irradiation and the prolonged irradiation time of the visible light which is associated with a vegetative growth, so that a nutritional component of the plant can stably be increased. Moreover, the lighting of the ultraviolet light source and the visible light source is controlled by the controllers, thus a user effort is reduced and efficiency is achieved.
