Fluid inclusions of the Kawarage and Ugusu silicified bodies were studied, in connection with the basic study of the hot spring-type gold mineralization. The Kawarage silicified body is formed in Miocene dacitic tuff and intruded quartz porphyry, mainly due to leaching of rock-forming materials except silica through hydrothermal activity. The Ugusu silicified body occurs in Miocene and Pleistocene andesitic lava and tuff. Acid hydrothermal alteration zones are not formed extensively around the Kawarage body but widely around the Ugusu body. Besides devitrified glass inclusions, abundant secondary fluid inclusions are found in quartz grains of the altered rocks in the Kawarage silicified body. They are mostly gaseous and liquid inclusions, but saline polyphase inclusions are also rarely observed. The coexistence of gaseous and liquid inclusions in a cluster, which suggests boiling phenomena of hydrothermal solutions, is occasionally found throughout the body but more commonly in the marginal zone. Homogenization temperatures of fluid inclusions are distributed in a range between 180°C and 290°C, but most frequently in ranges of 220°-230°C, 250°-260°C and 270°-280°C. The lowest homogenization temperature of the inclusion cluster which shows boiling phenomena, varies from 215°C to 285°C, and the depth estimated from the lowest one among these temperatures, i.e. 215°C, is about 230m. Some clusters having different boiling temperatures occur in the same specimen. This suggests that intermittent boiling of solution took place at various temperatures during the hydrothermal activity. Samples preferable to the measurement of homogenization temperature of fluid inclusion are very few in the Ugusu silicified body. A temperature range between 195°and 305°C with a high frequency range at 240°-285°C, was determined on a single sample. Boiling phenomena were recognized in a temperature range of 295°-305°C. Homogenization temperatures of fluid inclusions in an alunite sample range between 205° and 220°C, with a high frequency peak at 210°C. It is presumed from the present result that the thermal conditions of silicification in the Kawarage and Ugusu silicified bodies were similar to those of the Nansatsu-type gold deposits, but the reason why gold mineralization is not known in these two areas remains unsolved.