PURPOSE: To easily separate catalase and alcohol oxidase from each other in high efficiency by adding chitosan to a raw material liquid containing catalase and alcohol oxidase, thereby selectively precipitating exclusively alcohol oxidase.

CONSTITUTION: Chitosan with or without a water-soluble anionic polymer (preferably sodium polyacrylate) is added to a raw material liquid containing catalase, alcohol oxidase and a solid component originated from the raw materials or to a liquid produced by removing the solid component from the above raw material liquid. The alcohol oxidase is selectively precipitated by this treatment and the produced precipitate is separated from the catalase remaining in the liquid by conventional process.