The present invention provides soy sauce that comprises significant amounts of peptides, and, in particular, hypotensive peptide Gly-Tyr and hypotensive peptide Ser-Tyr, exhibiting a high degree of angiotensin-1-converting enzyme-inhibitory activity and has hypotensive effects while containing no hypotensive agent. Target soy sauce is obtained by mixing soy sauce koji having protease activity of 20 to 300 U/g koji with an aqueous common salt solution and subjecting the mixture to heated digestion, followed by compression filtration. Target soy sauce with a good flavor is obtained by adding soy sauce lactic acid bacteria and soy sauce yeast cells to the moromi mash after heated digestion, and subjecting the resultant to fermentation and maturation, followed by compression filtration.
