As part of a study of the reuse of waste okara (OC), a residue of soybean products and a kind of industrial wastes, a novel antioxidant food material was prepared in which OC fermented with Rhizopus oligosporus (OT) was combined with banana. A synergistic effect on the reactive oxygen scavenging activity (ROSA) between OT and banana was estimated using the method of photon emission scavenging of reactive oxygen by XYZ system, and the activity of a mixture of fermented OC and banana (OTB) 4/3 (OT: banana ratio 4 : 3 by weight) was found to be approximately 30 times that of OC alone. It was concluded that the effective ROSA of OTB is attributable to components in the extraction residue after extraction with 80% ethanol and water. OTB could be useful as a novel antioxidant food material and/or nutritional supplement.