The invention relates to a method and apparatus for preparing an ethanol/water mixture, in which fermentable raw materials (1) and the necessary auxiliary substances (2, 3) are fed into a reactor (4), the fermentable raw materials being selected from sugars and raw materials capable of being hydrolyzed into fermentable sugars; the raw materials are fed into the reactor (4), and the ethanol/water mixture is separated from the reactor fermentation solution in an evaporator (13); and non-fermented matter (6) is removed from the reactor. According to the invention, the reactor (4) fermentation solution is continuously being fed into a first falling-film evaporator (13) while the fermentation is going on; the ethanol/water mixture is evaporated in the first falling-film evaporator (13), and the evaporate (14) obtained from the evaporator (13) is condensed, and the condensed ethanol/water mixture is concentrated in a second falling-film evaporator (18), which is arranged in series with the first falling-film evaporator (13); from the second evaporator (18), water is removed as underflow (20); and non-volatile matter (15) is removed from the first evaporator (13) and is recycled to the reactor (4).