Abstract: Immobilized glucose isomerase preparation is prepared from microbial cells of Actinomycetes having glucose isomerase activity by the following procedures:A liquid culture of said microorganism is adjusted to a pH value of 6 to 9, heated to a temperature of 70.degree. to 80.degree. C., held for 1 to 20 minutes at the temperature and cooled rapidly. Then the microbial cells are harvested from the culture by filtration or centrifugation, frozen, subsequently thawed, and mixed with gelatin or sodium caseinate in an amount of 2 to 10% based on the dry substance of the treated cells. The mixture is kneaded to form a paste, which is impregnated in 0.2 to 1.0% glutaraldehyde solution in acetone to form a solid. Then the solidified material are separated from the acetonic solution by filtration without washing and finally dried to form immobilized glucose isomerase.