NOVELTY - The method of producing biofuel comprises generating monosugars by treating marine algae/polysaccharides extracted from marine algae with a hydrolytic enzyme and/or a hydrolytic catalyst, and fermenting the monosugars using a microorganism. The extraction of the polysaccharides is performed by soaking marine algae in an alkali aqueous solution and washing them with water, soaking the washed marine algae in an extraction solvent for a predetermined time and extracting saccharides such as agar, carrageenan and alginic acid, and separating the extract and collecting the remaining starch/fibrin.    USE - The method is useful for producing biofuel e.g. methanol and ethanol (claimed).    ADVANTAGE - The method of producing biofuel avoids the problem of raw material suppliance since it uses marine algae as a raw material for biomass and environmental problem such as soil erosion and contaminations, and reduces the production costs by excluding lignin eliminating process.    DETAILED DESCRIPTION - The method of producing biofuel comprises generating monosugars by treating marine algae/polysaccharides extracted from marine algae with a hydrolytic enzyme and/or a hydrolytic catalyst, and fermenting the monosugars using a microorganism. The extraction of the polysaccharides is performed by soaking marine algae in an alkali aqueous solution and washing them with water, soaking the washed marine algae in an extraction solvent for a predetermined time and extracting saccharides such as agar, carrageenan and alginic acid, and separating the extract and collecting the remaining starch/fibrin. The monosugar is produced by: reacting agar with the hydrolytic catalyst at 60-200 degrees C for 0-6 hours; reacting fibrin with the hydrolytic catalyst 80-300 degrees C; reacting fibrin with the hydrolytic enzyme for 0-144 hours; multi-step saccharification comprising reacting marine algae with the hydrolytic catalyst 60-300 degrees C for 0-6 hours; and the second or the third saccharification of the remaining fibrin or starch under the same reaction conditions. The marine algae are macroalgae such as red algae, brown algae and green algae, or microalgae such as Chlorella or Spirulina.    DESCRIPTION OF DRAWING(S) - The drawing shows a graph illustrating the ethanol production by B. custersii using hydrolyzate.