Peak positions and integrated intensities of diffraction X-ray are determined on the basis of X-ray diffraction measurement data output from an X-ray diffractometer, the number of determined peaks of the diffraction X-ray is counted, and analysis processing is started when the counted number of peaks reaches a preset peak number. The analysis processing is repetitively executed on the basis of X-ray diffraction measurement data. The peak positions and the integrated intensities of the diffraction X-ray are determined from the X-ray diffraction measurement data obtained from the start of the measurement till the analysis processing concerned, and qualitative analysis of collating the determined peak positions and integrated intensities with standard peak card data whose data base is made in advance and searching materials contained in a measurement sample, and quantitative analysis of determining the quantities of the materials contained in the measurement sample are executed.