This paper is the academic work to study Brecht’s “Theory of Behavior”. The theory of behavior is dealt with mainly in connection with Brecht’s story-collections, “The book of turning”, which has not yet been translated in Korean. It would be useful for this study to address Brecht’s moral concepts, for human behaviors are estimated by moral. Brecht doesn’t recognize moral as eternal and universal norms; moral must have a historical justification. In this context Brecht uses the term “Theory of Behavior” in place of moral. According to the theory of behavior, all the human behaviors are to estimate in the social or historical context and from the practical point of view. Conclusion: Brecht’s theory of behavior will provide a useful framework to estimate a variety of human behaviors.