Abstract: Method of separating heavy metals from complex-forming substance of aminocarboxylic acid type, or salts thereof in aqueous solutions, as well as a method of removing heavy metals from the solutions containing said complex-forming substance. A solution containing heavy metals in complex form and complex-forming substances of aminocarboxylic acid type is contacted with a ion exchanger having polyethyleneimine active groups, whereupon free non-complexed heavy metal cations are displaced out of said ion exchanger by an acid solution of 0.5-30 percent concentration, and the ion exchanger is converted back into its active form by a solution of an alkali hydroxide, carbonate, or hydrogen carbonate of 0.5-30 percent concentration.