A method of refining cellulosic biomass, including synchronous hydrolyzation of at least 85 wt % organic polymers, based on the total weight of the cellulosic biomass, in the cellulosic biomass into small molecular organic compounds. The synchronous hydrolyzation is catalytic hydrolyzation for which the catalyst used is a substance represented by L-M-S-H or L-M=S, wherein “M” represents metal, carbon or silicon, “S” represents a heteroatom, “L” represents one or more ligands, and “H” represents hydrogen.