Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is widely used for analysis of not only biological materials but also synthetic polymers. A mass spectrum obtained by MALDI-MS was found to have peaks at equal intervals on the m/z axis. The chemical structure of many types of biological compounds contain repeating units that have exactly the same elemental composition. If these repeated peaks could be identified based on the m/z interval value, such analyses could be optimized even further from the point of view of chemical structure. In this study, we describe a system for visualizing such data that has the capability of analyzing the repeated peaks on the m/z axis. The system, mzRepeat, was developed and evaluated by applying the mass spectrum of polyethylene glycol and mycolic acid, which was obtained using a JMS-S3000 Spiral-TOFMS system. Because mzRepeat can systematically show a mass spectrum that includes different numbers of repeating units, it has the potential for use in anlalyzing these types of molecules.