The present invention relates to an offshore disposal landfill leachate discharge system and leachate discharge method, and provides an offshore disposal landfill leachate discharge system and leachate discharge method, the offshore disposal landfill leachate discharge system being formed on the ground of the offshore disposal landfill in which both buried waste and water are present, and comprising: a plurality of catchment pipes in which a reactive medium for purifying water is embedded, and provided at the offshore disposal landfill; and a floating type water disposal device selectively connected to one or more of the plurality of catchment pipes, collecting water through the catchment pipes, purifying the same, and then discharging the same to the outside, wherein the water level of the offshore disposal landfill can be maintained at an appropriate value and the leachate, to be continuously generated at an offshore disposal landfill, can be purified and discharged to the outside.
