NOVELTY - A hydrothermal decomposer (41A) conveys the raw biomass material (11) from lower end side to inner portion of device main housing (42) by a conveyor screw (43). The pressurized hot water (15) is supplied to inner portion of main housing from upper end side so as to hydrothermally decompose biomass material. A lignin component and a hemicellulose component are transferred to pressurized hot water so as to separate the lignin and hemicellulose components from biomass material. A biomass solid content (17) is extracted from the upper end side of main housing.    USE - Apparatus for hydrothermally decomposing biomass used in manufacture of alcohol, petroleum substitution products, amino acids (all claimed), etc.    ADVANTAGE - Hexose liquid can be saccharified efficiently and various organic raw materials such as alcohol, petroleum substitution products, amino acids, etc., can be manufactured efficiently.    DETAILED DESCRIPTION - The obstruction of extraction hole of hot-water discharge liquid on the conveyance screw is prevented by a scraper. The pressurized hot water state is attained when the reaction temperature of apparatus is 180-240 degrees C. The weight ratio of biomass feedstock and pressurized hot water is 1:1-1:10. INDEPENDENT CLAIMS are included for the following:    (1) method for hydrothermally decomposing biomass, which involves supplying pressurized hot water to inner portion of main housing from upper end side so as to hydrothermally decompose biomass material; and    (2) organic raw material manufacturing system which includes enzymatic decomposition apparatus to perform enzyme treatment with respect to the cellulose in the biomass solid content extracted from the upper end side of main housing so as to obtain hexose. The enzyme treatment with respect to the hemicellulose component in the hot water discharge liquid is performed so as to obtain pentose.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the apparatus for hydrothermally decomposing biomass. (Drawing includes non-English language text)    Raw biomass material (11)    Pressurized hot water (15)    Biomass solid content (17)    Hydrothermal decomposer (41A)    Device main housing (42)    Conveyor screw (43)