An X-ray thin film inspection device of the present invention includes an X-ray irradiation unit 40 installed on a first rotation arm 32, an X-ray detector 50 installed on a second rotation arm 33, and a fluorescence X-ray detector 60 for detecting fluorescence X-rays generated from an inspection target upon irradiation of X-rays. The X-ray irradiation unit 40 includes an X-ray optical element 43 comprising a confocal mirror for receiving X-rays radiated from an X-ray tube 42, reflects plural focused X-ray beams monochromatized at a specific wavelength and focuses the plural focused X-ray beams to a preset focal point, and a slit mechanism 46 for passing therethrough any number of focused X-ray beams out of the plural focused X-ray beams reflected from the X-ray optical element 43.