NOVELTY - A strong acid (D) is added to slurry of cellulose biomass (A) to adjust pH of 1-3.5, hydrothermal-processed, primary saccharification decomposition of hemicellulose contained in the cellulose biomass slurry is carried out and sccharified to 5C pentasaccharide, steam (F) is added, secondary saccharification decomposition process of cellulose contained in the cellulose biomass is carried out and saccharified to 6C hexasaccharides, and secondary solid-liquid-separation process is carried out. The alcohol fermentation process is carried out, distilled, and concentrated, to obtain ethanol.    USE - Manufacture of ethanol used for decomposing cellulose biomass.    ADVANTAGE - The ethanol is economically and efficiently manufactured with suppressed usage amount of strong acid.    DETAILED DESCRIPTION - A strong acid is added to slurry of cellulose biomass to adjust pH of 1-3.5, hydrothermal-processed by supercritical state or subcritical state, primary saccharification decomposition of hemicellulose contained in the cellulose biomass slurry is carried out and sccharified to 5C pentasaccharide, and a primary solid-liquid-separation process is carried out for separating the slurry into solid and liquid. Steam is added to dehydrated cake, pressurized in a pressurized reactor, secondary saccharification decomposition process of cellulose contained in the obtained cellulose biomass is carried out and saccharified to 6C hexasaccharides, and secondary solid-liquid-separation process is carried out to separate the slurry into solid and liquid. The fermentation process in which alcohol fermentation (K) of saccharified liquid obtained in the primary and secondary solid-liquid-separation processes is carried out, the obtained fermented liquor is distilled, and ethanol is concentrated, to obtain ethanol.    DESCRIPTION OF DRAWING(S) - The drawing shows a flow chart explaining manufacture of ethanol. (Drawing includes non-English language text)    Cellulose biomass (A)    Strong acid (D)    Dehydrated cake (E)    Steam (F)    Slurry (G)    Alcohol fermentation (K)