To provide an X-ray fluorescence spectrometer capable of providing a stable fluorescent X-ray intensity regardless of the presence of irregularities or the like on a surface of a sample to be analyzed, the X-ray fluorescence spectrometer includes an X-ray source 1 including a primary X-ray limiting diaphragm 3. An aperture 3a of the primary X-ray limiting diaphragm 3 is of a shape effective to allow change in intensity of fluorescent X-rays 7 measured by a detector 8 to be not higher than 1% in the event that a height of the sample surface 5a relative to the X-ray source 1 and the detector 8 changes 1 mm at maximum.