The composition of a thin film measured by wavelength dipersive spectroscopy (WDS) deviates from the actual value if the film thickness is less than the X-ray generation depth of the elements measured. For multielement films, the measured concentration of the element with a shallow X-ray generation range is overestimated compared with that of the element with a deep X-ray generation range. In the case of lead zirconate titanate (PZT) films, the deviation of the measured composition ratio Pb/(Zr+Ti) from the actual value becomes more pronounced as the films become thinner. Accordingly, the composition measured by WDS needs to be calibrated for the film thickness. In this study, composition correction factors were derived theoretically as a function of the film thickness in order to calibrate the composition of thin PZT films obtained by WDS analysis. The thicknesses of films were calculated from the sum of [ ZAF] k of each element obtained in WDS analysis, and those values were compared with the experimental results.