NOVELTY - Production of ethanol, involves fermenting sugar-containing liquid obtained by biologically or chemically saccharifying biomass in fermentation tank, measuring temperature or ethanol concentration of the fermented liquid, extracting a portion of the fermented liquid, introducing the extracted liquid into vacuum evaporator evaporating the fermented liquid in vacuo to separate the evaporated gas containing ethanol, and returning the residual liquid (which has been cooled and having reduced ethanol concentration) to the fermentation tank.    USE - The method is useful for producing ethanol (claimed), preferably bioethanol useful as fuel or chemical compound.    ADVANTAGE - The inhibition of ethanol fermentation is prevented and ethanol can be produced cost-effectively with high yield. The ethanol contained in non-condensed gas is absorbed by water, hence ethanol yield is improved.    DETAILED DESCRIPTION - Production of ethanol, involves fermenting sugar-containing liquid obtained by biologically or chemically saccharifying biomass in fermentation tank, measuring temperature or ethanol concentration of the fermented liquid, extracting at least a portion of the fermented liquid from the fermentation tank, when the measured temperature or ethanol concentration reaches predetermined value or more, introducing the extracted fermented liquid into a vacuum evaporator evaporating the fermented liquid in vacuo to separate the evaporated gas containing ethanol, and returning the residual liquid (which has been cooled and having reduced ethanol concentration) to the fermentation tank. An INDEPENDENT CLAIM is included for ethanol producing apparatus, which comprises fermentation tank for fermenting the sugar-containing liquid, still for distilling the fermented liquid discharged from the fermentation tank, circulation cooling line for extracting a portion of fermented liquid in the fermentation tank, and carrying out external circulation, valve provided in the exit side of the fermentation tank, vacuum evaporator for evaporating the fermented liquid in vacuo to separate the evaporated gas containing ethanol, circulation cooling line for cooling the residual liquid in which ethanol concentration is reduced, concentration measuring unit for measuring the ethanol concentration of the fermented liquid, temperature measuring unit for measuring the temperature of the fermented liquid, and controller for controlling release of the valve and circulating the fermented liquid in the circulation cooling line.