Lipase from Candida cylindracea was modified with Hydrophilic/hydrophobic copolymer, polyalkylene oxide allyl ester - maleic anhydride copolymer. The modification reaction, maleylation occurs easily and effectively because maleic anhydride is very reactive chemical. The Degree of modification(DM) was varied by changing the weight ratio of copolymer to lipase over the range of 0.5 ~ 4 (w/w). Maximum DM was about 55% and the relative activity decreased as DM increased.