Characteristics of modified cellulases in organic solvents were studied. Cellulases modified with amphiphilic copolymer of polyoxyalkylene (POA)-derivative and maleic acid anhydride (MAA). Amino groups of the cellulase molecule were easily coupled with the MAA functional group of the copolymer. At the maximum degree of modification (DM) of 55%, the activity of modified cellulase retained more than 80% of the unmodified native cellulase activity. The modified cellulase using AKM-1511 with DM greater than 40% was found to be more than 90% soluble in aqueous solution of acetone and ethanol, leaving the native cellulase and impurities in the fermentation broth with the residue. Modified cellulase showed excellent stability against water-insoluble solvent. Moreover, cellulase modified with hydrophobic copolymer, which consists of ethylene oxide (EO) and propylene oxide (PO), could be dissolved in these solvents.