PURPOSE: To obtain a modified polyamide-polyamine having highly reactive amino and mercapto groups in the molecule and used as a curing agent for epoxy resin by reacting a polyamide-polyamine with a specified thiirane compound.

CONSTITUTION: A polyamide-polyamine compound is reacted with a thiirane compound of the formula (wherein R1, R2, R3 and R3 may be the same or different and are each H, alkyl or an aromatic group). Examples of the thiirane compound include ethylene sulfide, propylene sulfide, butylene sulfide and styrene sulfide. The polyamide-polyamine compound is obtained by the condensation of a polycarboxylic acid compound and a polyamine compound, an example thereof being a product of condensation of a polymeric fatty acid, such as a dimer or trimer acid, obtained by polymerizing a fatty acid having unsaturated bonds in the molecule with a polyamine compound, especially an aliphatic polyamine.