In the present invention, after tandem mass spectrometry is carried out for a single precursor ion in each micro area of an area for measurement and data is collected (S1), a plurality of product ions are extracted on the basis of the data (S2). For each product ion m/z, an MS imaging image is created (S3). Hierarchical cluster analysis is carried out on the plurality of MS imaging images, and the product ions are grouped on the basis of image similarity (S4). Product ions having similar distributions, that is, product ions classified into the same group, can be regarded as originating from the same compound. Thus, for each group, the intensity information for the plurality of product ions in each micro area is added (S5), and MS imaging images are created on the basis of the added intensity information (S6). As a result, even if a plurality of compounds overlap with the precursor ion, the effect of that overlapping can be removed, and images with better S/N ratios, sensitivities, and dynamic ranges than MS imaging images for a single product ion can be created and displayed.