The invention concerns a method for providing a high-purity n-butanol product stream from a crude n-butanol feed stream by fractional distillation in a dividing wall column (102) including an upper section (104), a middle section and a lower section (110), the middle section including an inflow section (106) and an offtake section (108) laterally separated from each other by a dividing wall (112) fixed in the column, the crude n-butanol feed stream being fed to the inflow section (106) and the high-purity n-butanol product stream being withdrawn from the offtake section (108), the liquid stream flowing out of the upper section (104) being collected and divided into a first liquid stream (114) and a second liquid stream (116), the first liquid stream (114) being fed to the upper region of the offtake section (108) and the second liquid stream (116) being fed to the upper region of the inflow section (106), wherein the split ratio between the mass flow rate of the first liquid stream (114) and the mass flow rate of the second liquid stream (116) is from 2:1 to 5:1.