NOVELTY - A sugar liquid manufacturing apparatus (110) has reaction tank which accommodates the mixture containing the polysaccharide, catalyst and water, stirring portion (252a) which stirs the mixture accommodated in the reaction tank, load measurement portion which measures the load stirred in the stirring portion, and concentration estimation portion which estimates the concentration of hydrolyzate of polysaccharide in the mixture based on the measured load, and hydrolyzes polysaccharide of lignocellulosic biomass-derived using a catalyst and manufactures sugar liquid.    USE - Sugar liquid manufacturing apparatus is used for manufacturing ethanol (claimed) e.g. bioethanol and biomass ethanol.    ADVANTAGE - The sugar liquid manufacturing apparatus controls reaction of hydrolysis.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) manufacture of sugar liquid, which involves accommodating mixture containing polysaccharide, catalyst and water in a reaction tank, measuring oxidation-reduction potential of mixture accommodated in reaction tank, estimating concentration of hydrolyzate of polysaccharide in the mixture based on measured oxidation-reduction potential, and controlling reaction of mixture in the reaction tank; and    (2) manufacture of ethanol, which involves using stirring portion which stirs the reaction tank which accommodates the mixture containing polysaccharide of lignocellulosic biomass-derived, catalyst and water, and mixture accommodated in this reaction tank, hydrolyzing polysaccharide, obtaining sugar liquid, fermenting the sugar liquid, measuring load which stirs the stirring portion, estimating concentration of hydrolyzate of polysaccharide in the mixture and controlling reaction of mixture in the reaction tank.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic view of manufacture of ethanol. (Drawing includes non-English language text)    Ethanol manufacturing system (100)    Sugar liquid manufacturing apparatus (110)    Ethanol manufacturing apparatus (120)    Hot water reaction portion (210)    Stirring portion (252a)