Overheating experiments on fluid inclusions were carried out using calcite, anhydrite and quartz sampled from geothermal fields. Fluid inclusions in calcite, anhydrite and quartz started to stretch at 55°C, 35°C and 100°C by overheating above homogenization temperatures, respectively. Fluid inclusions in quartz are stable within 100°C overheating, therefore quartz is considered to be the most suitable mineral for measurement of homogenization temperatures among the three minerals. When calcite or anhydrite are used for homogenization temperature measurement, it is recommended to measure one fluid inclusion in one thin chip of mineral or to measure fluid inclusions in order from lower homogenization temperature up to the temperature at which the inclusion starts stretching.