NOVELTY - The method involves performing spin dehydration of mixing vapor generated by distillation processing used for producing fermentation main product, using separation film. Feed rates of steam at vapor-liquid equilibrium critical point of fermentation main product and water in uppermost and lowermost portions of distilling column (5) are corresponded with each other. The feed rate of steam supplied to lowermost portion of distilling column is controlled to 90%-110% of target-steam feed rate, based on temperature change of uppermost portion of distilling column.    USE - Spin-dehydration purification processing method of fermented liquor such as ethanol fermented liquor or acetone-butanol fermentation liquid (both claimed) used as automotive fuel.    ADVANTAGE - Loss of fermentation main product can be prevented, and stable spin-dehydration purification processing of fermented liquor can be efficiently performed over a long period of timer at low energy consumption, without the need of performing complicated post-process in the bottom of the distilling column, as the concentration of fermentation main product in the bottom of the distilling column is set to be low, by controlling feed rate of steam supplied to lowermost portion of distilling column to 90%-110% of target-steam feed rate, based on temperature change of uppermost portion of distilling column, while providing global-environmental protection. Smooth dehydration process can be easily achieved, as superheat processing is performed before spin-dehydration using separation film, and hence the service lifetime of the separation film having heat resistance and solvent resistance characteristics can be improved. Mixing of acid to the fermentation main product can be reliably prevented by performing neutralization processing by adding alkaline component to fermented liquid before supplying to distilling column. Favorable dehydrating concentration performance can be easily achieved, as adhesion of impurity to the separation film is prevented.    DETAILED DESCRIPTION - Neutralization processing is performed by adding alkaline component to fermented liquid before supplying to distilling column. An INDEPENDENT CLAIM is included for spin-dehydration purification processing system that includes condenser for generating condensate, by condensing a portion of the mixing vapor sent out towards the spin-dehydration unit from the tower top of the distilling column. A condensate retention unit is positioned in the middle of the flow path of the mixing vapor inside the tower top portion of the distilling column, for retaining the condensate from the condenser, when fermented liquor vapor is passed through the condensate.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic view of the spin-dehydration purification processing method of ethanol fermented liquor. (Drawing includes non-English language text)    Fermentation ethanol purification processing system (1)    Undiluted solution tank (2)    Undiluted solution supply pump (3)    Distilling column (5)    Steam flow controller (6)