By regarding total precision of an X-ray intensity as counting precision due to statistical fluctuation and counting loss and by regarding the counting precision as a product of precision of an uncorrected intensity, which is an intensity before counting loss correction is performed, and a gradient of a corrected intensity with respect to the uncorrected intensity, a counting time calculation unit (13) included in an X-ray fluorescence spectrometer of the present invention calculates a counting time from specified total precision of the X-ray intensity, a given counting loss correction coefficient, and a given corrected intensity for each measurement line (5).