Provided is a method for producing a feed additive raw material that can be used as a raw material of a feed additive for improving the palatability of feed and is capable of stably culturing animalcules containing a large amount of amino acids. A method for producing a feed additive raw material, comprising: a first biological treatment step of preparing a first biologically treated liquid containing dispersible bacteria by introducing an organic wastewater containing 40 wt % or more of protein to a first biological treatment tank and performing aerobic biological treatment with bacteria； a second biological treatment step of preparing a second biologically treated liquid by introducing the first biologically treated liquid to a second biological treatment tank and performing activated sludge treatment； and a sludge separation step of taking out part of the tank sludge from the second biological treatment tank as the feed additive raw material.
