Mechano-chemical effects of natural and synthetic zeolites induced by a dry grinding process using a planetary ball mill, which can be classified as a high-intensity grinder, was studied by various analytical methods, e.g. X-ray diffraction (XRD), radial distribution function (RDF) analysis, infrared absorption spectroscopy, thermogravimetric and differential thermal analyses, and the measurement of cation-exchange isotherms. Both zeolites became to be in an amorphous state in terms of X-ray powder diffraction patterns within certain grinding periods depending on their components. Mordenite tended to be in an amorphous state easier than clinoptilolite. Taking into account the results of infrared absorption analysis, the network structure of channels of the ground zeolite sample seems also to be considerably deformed and/or destroyed. The effect of dry grinding was also found on the amount of dehydration and it seems to be attributed to the decrease in the amount of crystalline water by making cations in the channels labile. However, the specific surface area and the saturated amount of adsorbed cations for the ground samples still showed certain large values comparing to, for example, clay minerals. The significant change was not confirmed by the RDF analysis for the XRD patterns. These suggest that the channels were not completely destroyed at the microscopic level even by dry grinding for a long time.