A lighting system for preventing a plant disease damage (1) is provided with an ultraviolet light source (8) which emits ultraviolet ray including UV-B in a wavelength region of 255 to 340 nm, a visible light source (9) which emits visible light, and controllers (4, 5) which control a lighting of the ultraviolet light source (8) and the visible light source (9). The controller (4) controls the lighting of the ultraviolet light source (8) so that a horizontal irradiance on a canopy surface of a plant is 50 µW/cm 2 or less during a predetermined daytime period. The controller (5) controls the lighting of the visible light source (9) 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 (1) 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 (8) and the visible light source (9) is controlled by the controllers (4, 5), thus a user effort is reduced and efficiency is achieved.
