To increase radiation intensity of deuterium lamp with continuous spectrum in UV region including vacuum UV in order to enable the lamp to illuminate wide area in high intensity. A pair of electrodes 7 and 8 is covered with dielectrics, placed outside of a UV transparent tubular discharge vessel 1 and plunged into the discharge vessel 1. There is a shield box 2 with a separator 3 between the electrodes 7 and 8 in the discharge vessel 1. Deuterium gas, hydrogen gas, mixture gas with deuterium, or mixture gas with hydrogen is enclosed in the discharge vessel 1 as discharge gas. A slit 4 is formed on the separator 3 along the axis of the discharge vessel 1 in order to squeeze the discharge path arising between the electrodes 7 and 8. The slit 4 makes radiant points continuous and then the lamp length would not be limited. When sine wave in high voltage is applied between the electrodes 7 and 8, dielectric-barrier discharge is caused. Continuous spectrum UV light can be obtained to illuminate the wide area in high radiation intensity.