This article is an introduction to the theoretical study of the ''public sphere (= ?ffentlichkeit)"and information society. According to Nancy Fraser's explanation，the meaning of ''public sphere" is the modem theater in which citizens take part in the government through discussion as the media. The argument of ''public sphere"，which originates in the critical theory of Habermas，J. and Alent，H.，has been reconsidered in last 15 years. In 1989，''Strukturwandel der ?ffentlichkeit" was translated into English，and the themes of ''public sphere"，''possibility of its realization"，and its reality as a social communication channel，have been debated by American and English critical theorists. These days，some Japanese sociologists are discussing the possibility of ''public sphere" in the context of ''Internet community". In other words，there are two contexts in the recent reconsideration of the ''public sphere". One is the reevaluation of democracy (Ex: democratic revolution in eastem Europe); another is the ''grown up" information society. But，is the formation of the ''public sphere" really possible in the Internet-Age? What conditions would constitute the civil public sphere? This article tries to answer these questions by considering the critical argument for Habermas's concept of the ''liberal-public sphere".