PURPOSE: An aqueous solution containing fibroin and an enzyme is added to an aqueous salt solution to effect salting-out to obtain the titled enzyme which keeps high enzymatic activity with high stability and safety in an industrial scale in low costs.

CONSTITUTION: An enzyme or a plurality of enzymes such as arginase or phosphatase is added to 5W80wt% alkali metal salt solution containing 1W20wt% of fibroin obtained from silk or the like in an amount of 30wt% based on the fibroin protein, then the pH is adjusted with hydrochloric acid to prepare an aqueous fibroin solution containing enzymes. Then, the solution is poured in a stream as fine as possible into a coagulation bath of an inorganic salt such as sodium chloride and/or organic salt, 25W100wt%, saturated solution under violent agitation to precipitate immobilized enzymes in the form of foam or powder. Then, the precipitate is filtered, rinsed with water, dried, when needed, crushed to give the objective product.