Mold-preventive action of 15 kinds of compounds against soy sauce was examinined and it was found unexpectedly that none of them possessed marked action up to about 0.01% concentration. The compounds tested were as follows: Quinoxaline, pyrazine-carboxylic acid, methyl pyrazine-carboxylate, pyrazine-carboxyl amide, pyrazine-2, 3-dicarboxylic acid, dimethyl pyrazine-2, 3-dicarboxylate, pyrazine-2, 3-dicarboxylic acid diamide, pyrazine-2, 3-dicarboxylic acid dihydrazide, nicotinic acid, methyl nicotinate, nicotinic acid hydrazide, 2-chloro-6-methyl-4-isoamylresorcinol, 2-chloro-6-methyl-4-hexylresorcinol, 3, 3′-dicyclohexyl-4, 6, 4′, 6′-tetrahydroxydiphenyl, and agaricic acid trihydrazide.