The sanitary landfill method not only stops leakage of leachate and landfill gas to the outside, it also prevents water or air ingress. These methods significantly reduce the environmental contamination of landfills. Recently, landfilling of organic wastes such as sewage sludge and food waste has been forbidden, and landfilled wastes are dried. In addition, the water supply from outside is blocked, and the inside of the landfill remains very dry using the sanitary landfill method. At present, municipal solid-waste landfills have a generalized landfill-gas recovery and energy conversion. However, delayed decomposition of waste due to drying of the landfill will prolong the post-management period and reduce the amount of landfill gas after final disposal, which has a serious impact on the economics. In this study, a leachate recirculation facility was installed at the SUDOKWON landfill site in Incheon to prevent drying of the inside of the landfill. We investigated the effects of leachate recirculation on landfill gas evolution by observing the changes in water content and landfill-gas collection. As a result, the amount of landfill gas collected after recycling the leachate for about 34 months showed an increase of about 71% compared to the control. Therefore, the increase of water content through leachate recirculation greatly influences landfill-gas production, and it can increase the return from the landfill-gas energy project.