PURPOSE: To improve the efficiency of the reacting efficiency of peroxidase and the responsiveness and stability of an enzyme electrode by using an electrode material containing no medium, but true fungus peroxidase and oxidase in a double-enzyme system.

CONSTITUTION: An enzyme electrode is provided with a graphite bar 1 carrying a copper wire 2 stuck to one end of the bar 1 with epoxy silver 3 and the side face of the electrode is insulated with a polyethylene film 4. The other end of the electrode is polished to a spherical surface 5 so that a double-enzyme system cannot contain any medium, but true fungus peroxidase and oxidase. On the spheric surface 5 of the electrode covalently coupled with the true fungus peroxidase, a solution prepared by dissolving cholineoxidase in a phosphate buffer is confined with a dialysis membrane 7 and the membrane 7 is fixed with a rubber band 8. Consequently, the electrode is chemically modified and does not react to peripheral materials, because the electrode contains no medium. Therefore, the reactivity of the peroxidase is improved and the response of the electrode becomes faster and sufficiently stabilized.