NOVELTY - Apparatus for hydrothermal decomposition of biomass comprises solid biomass feedstock containing cellulose and hemicellulose from one side of apparatus main body; hot-water dissolution component; effective reaction region; and temperature-reduction region which makes temperature dive to the temperature as for which an excessive loosening does not have a hot-water dissolution component immediately after finishing an effective reaction region.    USE - The apparatus is useful for hydrothermal decomposition of biomass (claimed).    ADVANTAGE - While hydrothermally decomposing efficiently, in order to suppress the excessive solution of hot-water solubilization hemicellulose used as solubilized part, the excessive solution to hemicellulose can be significantly suppressed by providing the region which carries out a temperature reduction rapidly to the temperature to which an excessive solution does not advance from hydrothermal decomposition temperature.    DETAILED DESCRIPTION - Apparatus for hydrothermal decomposition of biomass comprises solid biomass feedstock containing cellulose and hemicellulose from one side of apparatus main body, where pressurized hot water is supplied from the other side, biomass is hydrothermally decomposed carrying out the opposition contact of both within an apparatus main body; hot-water dissolution component that is dissolved in a hot water, while discharging pressurized hot water from the one side of apparatus main body outside, biomass feedstock is made to discharge from the other side outside, it forms toward one side from the other side of an apparatus main body, the supply temperature of pressurized hot water is maintained for a fixed time, and is hydrothermally decomposed; effective reaction region; and temperature-reduction region which makes temperature dive to the temperature as for which an excessive loosening does not have a hot-water dissolution component immediately after finishing an effective reaction region. INDEPENDENT CLAIMS are:    (1) a manufacturing system of organic raw material using biomass feedstock comprising preprocessor which pre-processes the biomass feedstock of the solid containing cellulose and hemicellulose; biomass hydrothermal decomposition apparatus; first enzymatic-decomposition apparatus which carries out an enzymatic decomposition to the sugar liquid which enzyme-treats the cellulose in biomass solid content emitted from the biomass hydrothermal decomposition apparatus, and contains a hexose; and first fermentation apparatus which manufactures any one of alcohol, petroleum substitute items, or amino acids by fermentation process that is comprised using the first sugar liquid obtained with the first enzymatic decomposition apparatus; and    (2) a temperature control method of hydrothermal decomposition apparatus of biomass comprising while supplying the biomass feedstock of the solid which contains a cellulose and hemicellulose from the one side of an apparatus main body, pressurized hot water is supplied from the other side, biomass is hydrothermally decomposed carrying out the opposition contact of both, a hot-water dissolution component is dissolved in a hot water, while discharging pressurized hot water from the one side of an apparatus main body outside, the hydrothermal decomposition apparatus of biomass which makes biomass feedstock emit from the other side outside is used, while forming toward one side from the other side of an apparatus main body, maintaining the supply temperature of pressurized hot water for a fixed time and temperature-controlling in the effective reaction region to hydrothermally decompose, it temperature-controls in the temperature-reduction region which makes temperature dive to the temperature as for which an excessive loosening does not have a hot-water dissolution component immediately after finishing an effective reaction region.