PROBLEM TO BE SOLVED: To provide a method capable of effectively recycling organic waste liquid as a resource. A culture solution obtaining step for obtaining a culture solution for cultivating duckweeds from an organic waste solution； a first culture step for culturing duckweeds while adding the culture solution to a duckweed growth system； A duckweed comprising a second culturing step for cultivating duckweeds in a state where the amount of addition is reduced compared to the first culturing step, and a recovery step for collecting duckweeds after culturing after the second culturing step. To make organic waste liquid resource-rich. [Selection] Figure 10【課題】 本発明は，効果的に有機廃液を有資源化できる方法を提供することを目的とする。【解決手段】 有機廃液からウキクサ類を培養するための培養液を得る培養液取得工程と，培養液をウキクサ類生育系に添加しつつウキクサ類を培養する第１の培養工程と，培養液の添加量を第１の培養工程に比べて軽減した状態でウキクサ類を培養する第２の培養工程と，第２の培養工程を経た培養後のウキクサ類を回収する回収工程と，を含む，ウキクサ類を用いた有機廃液の有資源化方法。【選択図】 図１０
