A fish sauce is treated for (2) to (16) hours at a pH of (9.0) to (10.0), under a temperature of (40.degree. C.) or lower and under a reduced pressure of (80) to (180) Torr, and the pH is then adjusted, if required, to be (4.5) to (7.0), to thereby obtain a final fish sauce which contains specific odor components having specific values or less as determined by gas chromatography, and which thus contains an acceptable level of undesirable odor components.