NOVELTY - Method of manufacturing ethanol, involves adding produced sugar liquid into a fermenter, subjecting the liquid to ethanol fermentation within the fermenter continuously, calculating inconsistent degree of actual value of concentration of carbon dioxide which is generated during ethanol fermentation, calculating the predicted value of carbon dioxide concentration based on the actual value of sugar concentration of the sugar liquid, and determining the state of ethanol fermentation as unsatisfactory when the inconsistent degree exceeds the predetermined allowance.    USE - The method and apparatus are useful for manufacturing ethanol (claimed).    ADVANTAGE - The ethanol can be manufactured easily, rapidly and continuously with excellent quality, and increased yield.    DETAILED DESCRIPTION - Method of manufacturing ethanol, involves producing a sugar liquid from biomass feedstock, adding the liquid into a fermenter, subjecting the liquid to ethanol fermentation within the fermenter continuously, calculating inconsistent degree of actual value of concentration of carbon dioxide which is generated during ethanol fermentation, theoretically calculating the predicted value of the concentration of the carbon dioxide based on the actual value of the sugar concentration of the sugar liquid, and determining the state of ethanol fermentation as unsatisfactory when the inconsistent degree exceeds the predetermined allowance. An INDEPENDENT CLAIM is included for apparatus for manufacturing ethanol, which comprises fermenter for adding the sugar liquid, where the ethanol is fermented using yeast, carbon dioxide densitometer which measures the concentration of the carbon dioxide generated within the fermenter, and sugar concentration meter which measures the concentration of the sugar liquid. The actual value of the concentration of the carbon dioxide is measured by the carbon dioxide densitometer. The predicted value of the concentration of the carbon dioxide theoretically calculated based on the actual value of the sugar concentration of the sugar liquid using the sugar concentration meter. The inconsistent degrees of the concentration are calculated, when the inconsistent degree exceeds a pre-determined allowance. The state of the ethanol fermentation is equipped with control unit.