We prepared sponge cakes without eggs for egg-allergic patients. We prepared sponge cakes as authentically as possible by substituting Tukuneimo (Dioscrea Batatas Decne) for eggs. Baking powder (BP) was suitable as a leavening agent. The use of foam stabilizers (Taiyo Chemistry Co. : SP) resulted in a 50% reduction in the amount of Tukuneimo needed. The coloring of sponge cakes looked more authentic by adding vitamin B2. Adding cocoa or green tea powder masked the smell peculiar to Tukuneimo.