In this study experimental examinations were carried out in order to investigate the ground water condition to prevent the leakage of the compressed air from an unlined rock cavern as energy storage. As a result it was affirmed that the compressed air can be stored if the air pressure is lower than hydrostatic pressure around the unlined cavern, or, if the ground water flows with positive hydraulic gradient normal to the surface of the cavern. The finite element analysis, derived from the concept of the gasliquid two phase flow in the ground, applied to the investigation. The results reaffirmed the condition above mentioned and indicated that the numerical procedure proposed here is an effective tool to estimate the leakage of the air or gases from the storage caverns in the field.