PURPOSE: To obtain an enzyme immobilized membrane which obviates the exfoliation between a selective permeable layer and reinforcing material even if the membrane is immersed in liquid for a long period of time and which has hardly deterioratable characteristics by chemically binding the reinforcing material made of a high polymer and the enzyme to the layer which selectively permeates the resulted product of decomposition.

CONSTITUTION: Acetyl cellulose is dissolved by cyclohexanone and the soln. thereof is cast on a glass plate. The solvent is evaporated to form an acetyl cellulose membrane 7 having hydrogen peroxide permeability on the glass plate. A polyesther cloth 9 is placed on the membrane 7 and a liquid mixture contg. enzyme and crysslinking agent is dropped thereon to effect crosslinking reaction so that the enzyme and high polymer reinforcing material 8 are chemically bound to the selective permeable layer 7. The enzyme immobilized membrane 1 formed in such a manner is stripped from the glass plate and is air-dried. The membrane 1 is prepd. by utilizing the chemical bond and therefore, the generation of the exfoliation between the layer 7 and the material 8 is obviated even if the enzyme electrode is immersed in the liquid for a long period of time. The longer life is obtd. as the characteristics deteriorate hardly.