To provide a substrate irradiating apparatus by which a substrate to be treated can be irradiated uniformly with light from a bar-shaped dielectric barrier discharge lamp speedily without damaging the substrate even when the substrate is so large in size that is length exceeds that of the dielectric barrier discharge lamp.

This substrate irradiating apparatus is constituted so that the substrate P is conveyed and faced to the dielectric barrier discharge lamps 1a, 1b to irradiate the surface of the substrate P with ultraviolet rays from the lamps 1a, 1b. The length of the dielectric barrier discharge lamp in the longitudinal direction is made shorter than that of the substrate in the direction perpendicular to the conveying direction. At least two dielectric barrier discharge lamps are disposed so that the region of the substrate to be irradiated with the ultraviolet rays from one of the dielectric barrier discharge lamps is superimposed at least partially on the region of the substrate to be irradiated with the ultraviolet rays from the other. Light shielding means 4a, 4b are arranged in the superimposed region for shielding the ultraviolet rays from the respective lamps 1a, 1b so that the irradiation amount can be changed according to the lapse of the substrate conveying time.