Method for producing ethanol using cellulosic biomass as raw material

A method for producing ethanol using cellulosic biomass as a raw material, the method comprising:

• a saccharification/decomposition step of performing saccharification/decomposition of cellulosic biomass by bringing a slurry of cellulosic biomass into a supercritical or subcritical state;
• a fermentation step of alcohol-fermenting a saccharified solution obtained in the saccharification/decomposition step;
• and
• a distillation step of distilling a fermented liquid obtained by the fermentation step to concentrate ethanol, wherein
• in the saccharification/decomposition step, the slurry after saccharification/decomposition is flash-evaporated in a first flash tank so as to have a temperature of 150° C. to 200° C. (inclusive), and retention time, in the first flash tank, of the slurry after saccharification/decomposition is 3 minutes or less,
• the slurry after saccharification/decomposition, which is taken from the first flash tank, is further flash-evaporated in a second flash tank so as to have a temperature of 100° C. to 120° C. (inclusive), and
• a first flash steam generated from the first flash tank is used as a heat source in the saccharification/decomposition step or the distillation step.