A scanning X-ray fluorescence spectrometer includes a quantitatively analyzing device (18) which calculates the concentration of hexavalent chrome based on the fact that the peak spectroscopic angle, at which the maximum intensity is attained in Cr-Kα line (22), changes depending on the ratio of the concentration of the hexavalent chrome vs. the concentration of the intensity of the total chrome. A plurality of detecting device (23) having different resolutions as a combination of a divergence slit (11), a spectroscopic device (6), a receiving slit (20) and a detector (8) is provided such that when the change of the peak spectroscopic angle is to be detected, a detecting device (23B) having a higher resolution than that of the detecting device (23A), which is selected when the concentration or the intensity of the total chrome is to be determined, is selected.