NOVELTY - Method for producing ethanol, involves, processing cellulose biomass containing slurry by parallel saccharification fermentation process tank, separating unreacted biomass by solid liquid separator, transferring the process liquid containing enzyme and ethanol to a buffer storage tank, separating the liquid into ethanol containing layer and enzyme containing layer by product separation apparatus, transferring the ethanol containing layer into an ethanol storage tank, and recovering ethanol from the layer.    USE - The method is useful for producing ethanol.    ADVANTAGE - The method is cost-effective, rapid, stable, continuous and environmentally-friendly, and enables easy recovery of ethanol with high yield. The enzyme used in the process is reusable.    DETAILED DESCRIPTION - Method for producing ethanol, involves, (a) performing continuous processing of cellulose biomass containing slurry supplied from a substrate storage tank by parallel saccharification fermentation process tank which performs saccharification reaction using cellulose and fermentation reaction using microorganisms belonging to Issatchenkia, (b) separating unreacted biomass with a solid liquid separator from the slurry processed in the parallel saccharification fermentation process layer and returning the biomass to the parallel saccharification fermentation process tank, (c) transferring the process liquid containing enzyme from which the unreacted biomass was removed and ethanol to a buffer storage tank and storing the liquid temporarily, (d) obtaining predetermined quantity of stored liquid from the tank, and separating the liquid into ethanol containing layer and enzyme containing liquid layer by a product separation apparatus, (e) transferring the ethanol containing layer into an ethanol storage tank, and recovering ethanol from the layer and (f) returning the enzyme containing liquid layer to the buffer storage tank, where the enzyme containing layer and ethanol containing layer are separated using a reuse loop. The loop obtains predetermined quantity of storage liquid from the buffer storage tank and circulates the liquid as an enzyme source to the parallel saccharification fermentation process tank. The buffer storage tank supplies the storage liquid to the product separation apparatus at a flow volume which ensures flow rate and pressure of the storage liquid required for separation of the product.