The present invention relates to a printer, which uses a lamp with wavelength of below 300nm without almost emitting light as a light source, even though the electric force of the lamp is increased, any substrates will not distort due to being heated. An electric discharge lamp is a short arc type extra-high-pressure mercury vapor lamp in which a pair of electrodes is provided in an electric discharge container, wherein mercury of 0. 08-0. 30 mg/mm3, rare gas, and halogen are enclosed in the electric discharge container and a distance between electrodes is 0. 5-2. 0 mm, and the lamp contains a plurality of light of wavelength of 300 to 400 nm, but almost contains the light with wavelength below 300 nm. The electric discharge lamp extends along an optical axis of a reflector with a revolution paraboloid shape reflecting face wherein the pair of the electrodes are arranged so that a straight line formed by connecting the pair of electrodes, and the lights emitted from the lamp become parallel lights, wherein part of the lights are emitted from a light-emitting outlet directly, and the other part are emitted from the light-emitting outlet after the reflection of the reflector. A linear illumination area IA is formed on the substrate.