In recent years, a great deal of interest has been paid worldwide to the conversion of lignocellulosic biomass on the basis of its viable potential to produce alcohol fuels and other bio-based chemicals. Among three major components, cellulose, compared to lignin and hemicelluloses, is much more difficult to hydrolyze because it is a highly crystalline polymer of D-anhydroglucosepyranose units joined together in long chains by β(1,4) glycosidic linkages. Thus, depolymerization of cellulose into its glucose substituents is typically catalyzed by mineral acids or enzymes. We have carried out the hydrolysis of cellobiose as well as the hydrolysis of microcrystalline cellulose over solid acid catalysts including zeolites, Al-incorporated mesoporous materials, ion-exchange resins, sulfated zirconia, etc. As a result, solid acid catalysts were demonstrated to be sufficiently acidic to cleave a β(1,4) glycosidic bond in cellobiose whereas they showed no glucose formation due to the highly-ordered structure of cellulose. Hence, we have first regenerated cellulose by ionic liquids containing chloride anions and then hydrolyzed over solid acid catalysts, yielding glucose up to 44 mol%.