NOVELTY - Primary pre-hydrolysis-processes of biomass is performed by pressurization/heating conditions, to generate monosaccharide, oligosaccharide and furfurals, by feeding into apparatus by supplying raw material suspension (1) of biomass more continuously than the supply port of continuous primary hydrolysis apparatus. Acetogenic bacteria are cultivated within the cultivation tank (RE) by transferring the taken-out primary pre-hydrolysis-processing liquid to cultivation tank, to obtain acetic acid.    USE - Manufacture of acetic acid used as raw material for synthesizing resin and adhesive agent.    ADVANTAGE - The method efficiently enables manufacture of acetic acid.    DETAILED DESCRIPTION - Primary pre-hydrolysis-processes of biomass is performed by pressurization/heating conditions, to generate monosaccharide, oligosaccharide and furfurals, by feeding into apparatus by supplying raw material suspension of biomass more continuously than the supply port of continuous primary hydrolysis apparatus. Discharge of pre-hydrolysis-processing suspension is more continuously discharged than the discharge port of primary hydrolysis apparatus. The discharge is in the state which maintained the temperature and pressure of pre-hydrolysis-processing of the primary pre-hydrolysis-processing liquid separated from pre-hydrolysis-processing suspension in apparatus, from the intermediate extraction opening (G) provided with the solid-liquid-separator (S) in the intermediate position of the supply port and discharge port of primary hydrolysis apparatus. Acetogenic bacteria are cultivated within the cultivation tank by transferring the taken-out primary pre-hydrolysis-processing liquid to cultivation tank. The acetogenic bacteria are cultivated by maintaining the furfural concentration contained in the primary pre-hydrolysis-processing liquid supplied to the cultivation tank to 0.5 %mass or less, to obtain acetic acid.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic view of apparatus for manufacturing acetic acid.    Raw material suspension line (1)    Intermediate extraction opening (G)    Cultivation tank (RE)    Solid-liquid separator (S)    Valve (V)