PURPOSE: To make it possible to reduce the space for constituting the process and prevent clogging of membranes by a raw material mixture, by providing a cylindrical agitation device equipped with the membranes in a saccharification tank.

CONSTITUTION: A continuous saccharification tank 2' is provided with a pressurized air inlet 1, charging inlet of raw material, e.g. cellulose, enzyme and hydrogen, formed saccharide discharge outlet 7 and sludge taking outlet 8 and further a cylindrical agitation device 11 equipped with membranes 4 is provided in the tank 2'. The device 11 is rotated to discharge only the formed saccharide through the membranes 4 from the discharge outlet 7. On the other hand, the enzyme is preserved in the tank 2'. thus, the saccharification step is integrated with the saccharide solution separation and enzyme recovery step and therefore an enzyme recovery line can be omitted to reduce the space for constituting the process. The clogging of the membranes 4 by the raw material mixture can be prevented by rotating the membranes 4.