To provide an excimer light irradiation apparatus which carries out an efficient washing and can decrease an uneven washing even to a large-sized substrate in a washing apparatus of a liquid crystal panel glass substrate or the like using an excimer light.

The excimer light irradiation apparatus is provided with a blow off pipe spouting a gas at least containing an inert gas such as nitrogen in a lamphouse with a plurality of excimer lamps arranged in parallel, and is provided with a first replace space surrounded with the blow off pipe, an upper surface part of the excimer lamp, and a party wall of the lamphouse, and a second replace space surrounded with the blow off pipe, a lower surface part of the excimer lamp, and the substrate to be conveyed. The first replace space is formed by spouting the inert gas from the blow off pipe toward the first replace space.