PURPOSE: To obtain industrially in high efficiency a high-quality amidonitrile in good yield at a temperature higher than the melting point thereof under adjustment of the pH level of the reaction system within a specified range without being subjected to any load in terms of equipment.

CONSTITUTION: The objective amidonitrile of formula III is obtained by reaction between a fatty acid halide of formula I [R1CO is a 8-22C (un)saturated fatty acid residue; X is a halogen] and an aminonitrile of formula II (R1 is H or a 1-3C alkyl; R3 is a 1-5C alkylene) in water as solvent in the presence of a basic substance. In this case, the reaction is conducted at a temperature higher than the melting point of said amidonitrile within a pH range of 7.5 to 13. The basic substance is pref. a hydroxide or (bi)carbonate of an alkali(alkaline earth) metal.