Water-rock interaction under sub- and supercritical hydrothermal flow conditions has been carried out by using a flow-through type autoclave with a temperature gradient in order to predict the dissolution and precipitation behavior of granite. Reaction temperature ranges from 325 to 505°C. Dissolution of granite increased with temperature in the subcritical region (325-380°C) and decreased in the supercritical region (400-505°C).A precipitation dominant zone was recognized within the supercritical region. Elsewhere, quartz was the main dissolved mineral, and no distinctive dissolution of other minerals was observed. Depending on conditions of temperature and pressure, dissolution and precipitation phenomena in granite could be drastically changed due to properties of the fluid such as 'liquid-like' and/or 'vapor-like' regions under supercritical condition.