To produce the fish processing residues small in the contents of trimethylamine oxide, trimethylamine and dimethylamine and low in a K value by treating the amines massively contained in the thermally treated fish processing residues with a specific microorganism.

This method for producing the fish processing residues low in the contents of trimethylamine oxide, trimethylamine and dimethylamine and low in a K value comprises simultaneously degrading the amines contained in the fish processing residues heated and ground in a station for treating fish guts and bones with Aspergillus sojae A-1 strain strong in forces for degrading amines and separated from a unrefined say sauce or with Aspergillus sojae B-1 strain subjected to a mutation treatment using UV light and strong in forces for degrading amines.