Abstract: A block copolyamide having effectively improved impact strength is obtained by polymerizing a mixture comprising substantially from about 50 to about 95 parts by weight of lactam and from about 50 to about 5 parts by weight of polyol in the presence of catalyst for an anionic polymerization and activator represented by the following formula (I); ##STR1## wherein A denotes a bifunctional organic residue having at least one kind of heteroatoms selected from the group consisting of N, O, S, F, Cl, Br and I, and Y and Y' denote an acyl group selected from the group consisting of ##STR2## respectively, and n and n' denote an integer of 3 to 11 respectively, or by polymerizing, in the presence of catalyst for anionic polymerization, a mixture comprising substantially from about 50 to about 95 parts by weight of lactam and from about 5 to about 50 parts by weight of prepolymer obtained by a reaction of polyol and activator represented by the above formula (I), wherein A denotes a bifunctional aromatic residue having