TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Components: The hydrothermal decomposition portion conveys the supplied biomass feedstock upwards by conveying unit inside apparatus main portion from below, supplies pressurized hot water to inside of apparatus main portion from upper direction side different from the supply location of the biomass feedstock, hydrothermally decomposes while carrying out counter contact of the biomass feedstock and the pressurized hot water, transfers hot water dissolution component into hot water discharge liquid which is the pressurized hot water to be discharged, and separates lignin component and hemicellulose component out of the biomass feedstock. The system further comprises pH meter measure apparatus for measuring pH of slurry like biomass solid content provided in downstream side of the slurry tank. The system further comprises first solid-liquid separator for separating biomass solid content which is provided in the downstream side of the slurry tank, and removing moisture content from slurry like biomass solid content. The system further comprises first saccharification tank for saccharifying biomass solid content separated from the first solid-liquid separator. The system further comprises first return line for returning water separated from the first solid-liquid separator to the slurry tank. The system further comprises second saccharification tank for saccharifying hot water discharge liquid from the hydrothermal decomposition portion. The second saccharification tank saccharifies the hot water discharge liquid from the hydrothermal decomposition portion and separates water from the first solid-liquid separator, which is mixed with the hot water discharge liquid. The system further comprises enzyme liquefaction tank for adding enzyme to biomass solid content separated with the first solid-liquid separator, and carrying out enzyme liquefaction. The system further comprises third saccharification tank for saccharifying the slurry like biomass solid content. The system further comprises second solid-liquid separator for separating solid portion from the sugar liquid after saccharification, and first moisture content separation apparatus for removing water from the sugar liquid after solid separation. The second saccharification tank saccharifies the hot water discharge liquid from the hydrothermal decomposition portion. The system further comprises third solid-liquid separator for separating solid portion from the sugar liquid after saccharification by the second saccharification tank. The system further comprises second water separation apparatus for removing water from the sugar liquid after solid separation. The system further comprises second return line for returning the water separated from the first water separation apparatus or second water separation apparatus to the any one or both of cooling unit of the slurry tank or temperature control unit of the hydrothermal decomposition apparatus. The water separated from the first water separation apparatus or second water separation apparatus is made into pressurized hot water by pressurization/heating unit, and has third return line which returned it to the pressurized hot water of a hydrothermal decomposition apparatus. The system further comprises biological treatment apparatus on the first return line, second return line, or third return line. Preferred Method: The enzyme liquefaction of the biomass solid content is carried out at upstream flow side which carries out enzyme saccharification of biomass solid content from which water is removed. EXAMPLE - No suitable example given.