To perform the fractionation and purification of an aromatic polyamine mixture by a simple means so as to afford the corresponding isomers in a pure or concentrated form.

The fractionation and purification of a diphenylmethane-based polyamine mixture are performed according to the following process: (a) in the 1st extraction step, a polyamine starting mixture is mixed with a two-phase system composed of (i) a hydrophobic solvent phase and (ii) an aqueous phase and subjected to countercurrent treatment to effect separation into the 1st aqueous phase and the 1st organic phase; (b) the 1st organic phase is subjected to multistage distillation and separated into (i) the 1st fraction containing an auxiliary amine, (ii) the 2nd fraction containing the hydrophobic solvent and (iii) distillation residues comprising the 1st polyamine fraction; (c) in the 2nd extraction step, the 1st aqueous phase is subjected to extraction using a solvent phase comprising the hydrophobic solvent and the auxiliary amine and separated into (i) the 2nd aqueous phase with reduced amine content and (ii) the 2nd organic phase; and (d) in a distillation step, at least part of the 2nd organic phase is separated into (i) the 1st distillate comprising, the hydrophobic solvent and the auxiliary amine and (ii) distillation residue comprising the 2nd polyamine fraction.