Abstract: An x-ray microanalyzer is a useful instrument which obtains an image representing the distribution of the constituent elements of a specimen, by detecting characteristic x-rays produced from a microscopic region on the specimen. The present invention is intended to enhance the efficiency of such an analysis of a specimen using an x-ray microanalyzer. A region of interest is designated upon the aforementioned image. The average weight concentration of the constituent elements in this region or information about the distribution of signal intensities is quickly obtained.