In order to research the origin of taste of so-called "delicious natural water", chemical components of tap and natural water samples were measured and compared to each other. The values of pH, carbonate ion, KMnO4-consumed values and ion levels in the samples were determined by the officially established methods for drinking water. Twenty-one kinds of tap water samples were collected from the domestic water supply of Hyogo, Osaka and Nara prefectures. On the other hand, 10 kinds of natural water samples were collected from Hyogo, Osaka and Nara prefectures, while the other 11 samples purchased at markets were originated from several parts of Japan. The tap water samples gave significantly higher values on the KMnO4-consumed values and the concentrations of chloride and sulfate ions and iron (Fe2++Fe3+) than the respective data in the natural water samples. In contrast, the concentrations of carbonate ion in the natural water samples were significantly higher than those in the tap water samples.