An essential feature of the qualitative analysis of the powder X-ray diffraction (PXRD) method is that this provides information on the sample’s crystal structure, which often affects the properties and functions of the material. The qualitative analysis by the PXRD method is a phase identification method based on the matching of known patterns (Card) in with measurement patterns. Tips in the phase identification procedure are the quality of the measurement data, the presence of trace phases, and the selection of card. In recent years, the performance of analysis software has been improved, and phase identification can now be done quickly and easily by a computer search. Since the results of computer searches are not always correct, analysts need to evaluate the validity of the analysis results themselves.