Strong opposition to the dominant culture after the Second World War in the 20th century occurred in the USA and Europe in the 1960\'s and 1970\'s and such social changes influenced greatly on the change of performance types. This thesis focuses on the Living Theatre that showed the most radical theater type among them. Living Theatre is the representative theatrical company that showed typical participation in social problems, raising opposition to the traditional dramas by reflecting the US social situations with active students\' movements in those days. Its members attached importance to the message delivering plain and principle political assertions, development methods that led to audiences\' participation and expressions through the actors\' body. In such ways, they became a typical US avant-garde cinema in the 1960\'s and 1970\'s and various techniques being introduced and applied by them became the regular theatre style in the 1960\'s and 1970\'s. In this thesis, in order to understand activities of theatrical companies, the researcher also inspects theatrical concepts and assertions of Antonan Artaud who is acknowledged to come in contact with Nietzche\'s artistic directions and genealogy. Although he couldn\'t realize them on the stage in his days, his theatrical concepts and assertions would be greatly helpful for grasping the substance of modern experimental theatre concretely.