To obtain the subject new surfactant little in irritativeness against skin by using a specific amine as a base constituting a counter ion.

This anionic surfactant uses a compound of formula I [R1 to R5 are each a hydroxyalkyl; R6, R7 are each an alkylene; (m) is the number of 0, 1 or larger] as a base constituting a counter ion. The compound of formula I is obtained by adding an alkylene oxide such as ethylene oxide to a (poly) alkylenepolyamine such as ethylenediamine or tetraethylenepentamine. An long chain acyl group-containing anionic surfactant such as an acylated peptide of formula II [R is a hydrocarbon; R' is an amino acid side chain; (n) is ≥2] is preferable as the acidic residue of the objective surfactant. The surfactant can easily be obtained by neutralizing the base of formula I with the acidic residue of an anionic surfactant represented by the above-described surfactant in a solvent-free state or in an aqueous solution or the like.