The invention relates to an aromatic amine resin comprising a mixture of aromatic amine compounds represented by the following general formula (a): ##STR1## wherein A represents a phenylene, alkyl-substituted phenylene, diphenylene, diphenyl ether or naphthylenyl group, R.sup.1 represents a halogen atom or a hydroxyl C.sub.1-4 alkoxy or C.sub.1-5 alkyl group, l is 1 or 2, m is 0, 1, 2 or 3, n is an integer from 0 to 300 and when m is 2 or 3, the R.sup.1 group may be same or different and may join to form a 5- or 6-membered alicyclic moiety which may optionally contain one or more side chains, and also relates to processes for producing the same and a thermosetting composition containing the same.