In order to utilize tobiko (fly powder of konnyaku) as a food material, untreated powder (S), powder S soaked in ethanol and then ultrasonically irradiated for 15 min (A), and powder S soaked in ethanol for 15 min (B) were added to sponge cake mixture, and the effects on the physical properties, sensory characteristics, chemical composition and preservation of the cooked sponge cake were studied. Compared with the control product (no added tobiko), the sponge cake with up to 7.5% of material A added to wheat flour resulted in a brownish color, the cake having a small pore size, softness and an elastic texture. A sensory evaluation gave an equal rating to that of the control product. The cake was richer in nutrient content such as protein, dietary fiber and mineral components than the control product and showed favorable results in the preservation test. The addition of tobiko thus enhanced the quality of sponge cake.