PURPOSE: To provide the titled curing agent of low viscosity at low temperatures, good in compatibility with epoxy resin, long in pat life, capable of giving cured products of both high water and chemical resistances, containing an 1-alkyl-2-phenylimidazole.

CONSTITUTION: The objective curing agent containing an 1-alkyl-2- phenylimidazole of formula I (R' is 1W6C alkyl; R2 is H or 1W4C alkyl) (e.g., 1-ethyl-2-phenylimidazole). The compound of the formula I can be prepared by dehydrogenation of an imidazoline compound formed from an N-alkyl- ethylenediamine of formula II and a nitrile compound of formula III.