PURPOSE: To obtain an N-long chain acylamino acid salt having good color phase and flavor by hydrolyzing a specific amide-nitrile in the presence of a base followed by treatment with a metal hydride using inexpensive feedstock with industrial advantage.

CONSTITUTION: An amido-nitrile of formula I (R1 CO-is a fatty acid resmdue of 8-22 carbon atoms; R2 is H, a 1-3 C alkyl; R3 is a 1-5C alkylene) is hydrolyzed in the presence of a base and the resultant N-long chain acylamino acid of formula II (M is a cation) is treated with a metal hydride to give this amino acid salt. In a preferable embodiment, the metal hydride is an alkali borohydride and the treatment is conducted at 10-90°C.