The appropriate kind of polyurethane foam for immobilization of Aspergillus niger G153 spores is high density and open structure foam. The high efficiently immobilized mycelia can be prepared by cultivating 1.0-2.5x10 8 immobilized spores per 1 gram of polyurethane foam for 40 hours. The production medium containing 25 grams of glucose per 1 liter without adding any nitrogen source is suitable for gluconic acid production in shaking culture. In bubble column, the suitable conditions for the production are : the production medium containing 50 g/l of glucose in starch hydrolysate and tap water, 9 vym aeration rate, 200 g. of polyurethane foam per 1 liter of the production medium. It is possible to make 12 repeated batches with slightly decreasing in the yield of each batch. The examination of the mycelia growth by scanning electron microscope shows that mycelia grow at the suface of polyurethane foam and 0.45-0.8 mm. depth from the surface. The immobilized mycelia can retained thier activities after storing at 6 ํC for 7 days.