The study area for this research is a volcanic terrain in west Java, Indonesia. A three dimensional model was developed to explain the geothermal mechanism in the study area. This is because when we consider using geothermal energy, it is very important to analyze how groundwater flows and how heat is transported in the underground. Geological components of this area are mostly volcanic products such as pyroxene andesite, tuff, volcanic breccia, and basaltic lava. Hot springs were found in the west part of the study area. It is confirmed that there is a fault near hot springs, and also hot springs are on the boundary of different geological components. Development of the model and numerical simulation were carried out using the FEFLOW simulator. FEFLOW calculates groundwater flow, mass concentration and heat transport by finite element method. Electrical resistivity surveys were conducted in the study area, and the structure of the model was based on their results. The model covers an area of about 180 km2 and consists of 30 layers. Thickness of each layer was 0-160 m depending on the location. Stable isotope ratio of oxygen is also included in modeling to confirm that the developed model is accurate by comparing calculated value of δ18O with measured value. Numerical simulation clarified the groundwater flow and heat transportation in the study area.