The purpose of this research is to clarify groundwater behavior in discontinuous or jointed rock mass. A simplified regularly jointed rock mass model (2m long, 1m high) was constructed to check the movement of water and distribution of water pressure. A finite element code has been developed to determine the hydraulic behavior of jointed rock masses. The joint was recognized as a main conduit for water flow. The new code was verified by the results of experiments for the model. The distribution of water pressure and position of free surfaces are well predicted by the code.