[Problem] To provide a method for manufacturing organic fertilizer, which can convert large quantities of livestock excrement into organic fertilizer efficiently and over a short period of time using housefly larvae. [Solution] This method for producing organic fertilizer comprises: a fodder preparation process in which rice hulls (54) and bean curd refuse (55), which promote the feeding habits of larvae, are mixed into excrement (18) to prepare fodder (19)； a fodder storage process in which a predetermined quantity of fodder (19) is stored in a fodder storage tray (20)； an egg introduction process in which housefly eggs (51) are introduced into the fodder (19) stored in the storage tray (20)； and a fertilizer base material preparation process in which the fodder (19) stored in the storage tray (20) is fed to the larvae that have hatched from the eggs (51), thereby raising the larvae, and the fodder (19) is subjected to enzymatic breakdown inside the larvae in the process of raising the larvae, and is excreted from the larvae, to produce organic fertilizer.
