PROBLEM TO BE SOLVED: To recycle a food-derived waste liquid, which has hitherto been incinerated or discarded, into organic fertilizer or the like by using earthworms without incinerating or discarding it.SOLUTION: Earthworm culture soil 3 containing wood fragments or the like into which the food-derived waste liquid has been absorbed is laid on soil partitioned by a frame body 2. Then, food residues 4 are spread on the laid earthworm culture soil 3 and digested by the earthworms. At the same time, the activity of soil microorganisms is promoted by the excrement of the earthworms, and the food residues 4 and the earthworm culture soil 3 are decomposed by the soil microorganisms to form earthworm decayed soil. Then, after the earthworm decayed soil is taken out, the fresh earthworm culture soil 3 is laid, and the following procedure is repeated: spreading the food residues 4 on the earthworm culture soil 3, decomposing the food residues 4 and the earthworm culture soil 3 to form the earthworm decayed soil, and taking out the earthworm decayed soil.
