Apparatus for a photo-induced process are provided, which implement a transparent film (instead of an optical window), to reduce light absorption loss that would result from use of an optical window. A photo-induced process apparatus eliminates problems of conventional systems which use optical windows, such as blurring an optical window and the surface of a light source, photo absorption loss due to the optical window and/or a purge cleaning gas, and dust generation by a moving part such as a flexible curtain. A photo-induced process apparatus efficiently utilizes light emitted from a light source.