This invention provides a system for producing organic fertilizer from excreta of domestic animal obtained by digesting of larvae belonging to Diptera such as Musca domestica (housefly), Boettcherisca peregrine and Tabanus, and for producing grown larvae which can be used as a feed for cultured fish and chicken raising. In an embodiment, the system for producing organic fertilizer from excreta of domestic animal and for producing grown larvae which can be used as a feed for cultured fish and chicken raising is characterized by arranging a plurality of nurturing-processing storage units for nurturing larvae hatched from eggs, and a means for dislodging only larvae forcibly from a former nurturing-processing storage unit to a later nurturing-processing storage unit successively with the progress of growth of larvae, wherein larvae leave said former nurturing-processing storage unit autonomously.
