When large earthquakes occur over wide areas, in addition to damage to medical facilities, the disaster response capabilities of local governments are severely compromised. There is a very high possibility that the supply–demand balance of medicines will collapse within the disaster area, and that appropriate supplies of medicines will not be provided to disaster victims. Therefore, it is important to estimate in advance the quantity of pharmaceuticals that may be needed during disasters. In this study, the purpose is to clarify the quantity and quality of pharmaceuticals used by chronically ill patients by using Japanese National Health Insurance data regarding the issues mentioned above. The methodology used was to extract the status of pharmaceutical prescriptions based on receipt information from National Health Insurance data for Hakui, Ishikawa Prefecture, a small regional city in Japan, as the analysis target area. Through the analysis in this study, the quantity and quality of medicines supplied to chronically ill patients in Hakui, Ishikawa Prefecture, were clarified on a town-by-town basis.