To produce the subject surfactant capable of manifesting essential surface-active performances and useful as cosmetics, etc., by carrying out the neutralization under specific temperature conditions.

When (A) a tetracarboxylic acid is neutralized with (B) a base (e.g. a mono- or a bivalent alkali metal ion), the neutralization is carried out at ≤50°C, preferably ≤40°C, more preferably ≤30°C. For example, the component B is used in an equivalent amount of 2-4 times based on the component A. The above surfactant is preferably produced by placing the tetracarboxylic acid which is represented by the formula and is a precursor of a carboxylic acid type two-chain two-hydrophilic group-containing anionic surfactant in water containing sodium hydroxide, heating the resultant mixture at 50°C, stirring the mixture for 1 h, then allowing the mixture to stand at ≤0°C and removing water by using a freezing machine.