Abstract: A casing for a laser device in which contaminants do not generate even if it is radiated with laser light, a production method and a cleaning method of the same are provided. For this purpose, the cleaning method is a method of cleaning a casing (19) for an ultraviolet laser device, an inside of which laser light (11) passes through, comprises the steps of purging the inside of the casing (19) with an inert gas, and radiating F2 cleaning laser light (16) oscillated from an F2 molecular laser light radiating device (15) to the inside of the casing (19) to thereby remove contaminants adhering to the inside of the casing (19).