”Insanity” is considered the major theme of avant-garde theatre after Second World War. The elements of insanity also appear frequently on the Theatre works of Suzuki Tadashi, who was known as one of the most important artists of postwar avant-garde theatre movement in Japan. This paper discusses Suzuki Tadashi's theatrical theories by analyzing his works. Through cross-examining his works and theories, it is shown that the ”insanity” is not the contents of Suzuki's drama but the result of his language strategy of dramatic narrative. By destructing the text and roles in his works, the function of symbolic reference on stage is disrupted, meanwhile the metalanguage of drama was created as well. Suzuki Tadashi's distrust to the text and the desire to destruct the function of the role are deeply rooted to his repulsion of Japan's westernization started since Meiji Restoration.