An open chamber-type X-ray fluorescence analysis apparatus is provided to analyze a large-sized sample located outside the open chamber. The apparatus has a helium inlet provided in the open chamber for injecting helium gas into the chamber to replace gas within the chamber with helium, a film attaching/removing mechanism for covering the opening in the chamber with a film having high transmittance with respect to X-rays, and a gas outlet provided in the chamber for allowing gas to exit the chamber.