Functional copolymer-modified cellulase was applied to newspaper reprocessing. The new copolymers, composed of polyalkylene oxide (PAO) and maleic acid anhydride (MA), were synthesized to modify the cellulase. MA was attached to PAO allyl ester, formed by the reaction between PAO allyl alcohol and lauric acid. The modification is produced by the ability of MA to react with the amino acid group of the cellulase for modification. At the maximum degree of modification of 52%, modified cellulase showed more than 65% activity over the unmodified native cellulase. When modified cellulase was applied to the waste paper reprocessing, it was found that the cellulase enhanced the detachment of ink particles from paper. PAO was found to also cause the removal of the detached ink particles by floatation. This process creates a more moderate environment than conventional methods, improves the physical properties of the paper such as freeness and whiteness in comparison to conventional NaOH methods, while maintaining the same ink particle removal ability.