In recent years, the critical theory of the so-called 'Frankfurt School' has been mainly developed by Jurgen Habermas. He has succeeded to the problems of the "critique of instrumental reason" and of the "possibility of immanent critique", which were the principal tasks of the first generation of Frankfurt philosophers, and he has investigated a critical social science as a critique of ideology. In a technically advanced capitalist society, ideology is regarded as a systematic distortion involved in our ordinary communication. Habermas's critical theory is, therefore, grounded on a normative structure of a communication oriented to the idea of genuine consensus. This theme has been expanded and clarified in relation to a conception of what Habermas calls 'universal pragmatics'. In this paper, I concentrate on this 'universal pragmatics' and intend to study a significance of language in the critical theory. First, I briefly illustrate the basic perspective of Habermas's critical theory. Secondly his 'universal pragmatics' is discussed, and explained in the condition called the 'ideal speech situation' under which rational consensus is possible. And finally, the logic of discourse which grounds them is examined. In these examinations, it will be clear that Habermas attempts a new pursuit of the "possibility of immanent critique."