Natural gas hydrate that exists in the sediment is thought to constitute a large natural gas reservoir and is expected to be an energy resource in the future. In order to make recovery of natural gas from hydrates commercially viable, hydrates must be dissociated in-situ. Inhibitor injection method is thought to be one of the effective dissociation method as well as depressurization and thermal stimulation. In this study, dissociation behavior of an artificial hydrate core sample in inhibitor aqueous solution (methanol aqueous solution) was investigated experimentally. A newly constructed experimental set-up equipped with core holder achieves to investigate the dissociation behavior of hydrate core sample under similar condition under seafloor. Warm inhibitor aqueous solution is injected into the core sample. The heat supplied by the solution dissociates hydrate. Experiment is carried out varying the temperature and concentration of inhibitor. As a result, it becomes clear that inhibitor that changes the hydrate stability condition accelerates the hydrate dissociation rate effectively. Additionally specific feature that temperature of solution from outlet of core changes continuously, while outlet temperature does not change in case of pure water. This result suggests that the inhibitor concentration around hydrate surface should change continuously.