The production of various mineral waters has steadily increased in contemporary society. The purpose of this study was to evaluate the quality of one variety of mineral water “Tokiwa No Meisui” produced in Ina-city, Nagano Prefecture, Japan. Three different kinds of water were analyzed by the objective index of drinking water mineral valance: raw “Tokiwa No Meisui” water, PET bottled “Tokiwa No Meisui” water and city water in Ina City. To evaluate water quality objectively, we quantified the elements contained in the water samples. Samples were assessed not by the usual sensory evaluation but with the evaluation approach advocated by Hashimoto et al. which employs the Water Index of Taste （O-Index） and Water Index of Health （K-Index）．These three varieties were also compared in terms of the “Prerequisites for Tasty Water” and the “Standards for Tasty Water” devised for city water by the “Tasty Water Research Association” of the former Japanese Health and Welfare Ministry. The raw water and PET bottled water for Tokiwa No Meisui showed an O-index of OI ≧2.0 and KI ≧5.2, which we classified as tasty/healthy water. The tap water from Ina-city can be classified as tasty water due to its values of OI ≧2.0 and KI< 5.2. In general, the raw water and PET bottled water of Tokiwa No Meisui met the “Standard for Tasty Water” and “Prerequisites for Tasty Water”．In recent years, Tokiwa No Meisui has consistently been awarded prizes such as the Monde Selection Gold Award and the Superior Taste Award（iTQi） based on sensory evaluation. In this study, we showed that “Tokiwa No Meisui” is a delicious （and healthy） variety of mineral water through an objective index to evaluate the mineral balance of drinking water. In conclusion,“ Tokiwa No Meisui” was evaluated as good water to drink.