Since 1925, from last years of Taisyo to early years of Showa, a movement of pure oral method appeared on the stage of deaf school. An idea of pure oral method is that signs must be prohibited and only speech is encouraged in the education of deaf children. This way of thinking took place more and more popular in Japan. At the same time, signs were strictly banned in every deaf school, because of being an obstacle for acquiring oral language. But teachers of Osaka City school for the Deaf insisted on using sign language. They began to defend against an attack of pure oralists. They organized a group for the study of sign language. Some of them also set up Kurumaza Theater of Drama. Why they defend against rigid pure oralist to use sign language? We concluded that (1) the principle of the Osaka City School was cultivation of religious mind, and teachers thought life of deaf children and communication of deaf people very important. There are many deaf staff in the member of teachers. (2) some of teachers were enthusiastic for Drama Art. In drama, sign language was necessary for its expression. Mr. Matsunaga, one of teachers, mentioned that substance of deaf people\u27s drama is different from hearing people