The aim of this study is to develop a computational method of discourse analysis based on corpus semantics. The objective is to achieve an accurate understanding of the debate content and structure through hypotheses generation. As for verifying the hypotheses, the topic extraction and semantic similarity evaluation from the public debate minute corpus is examined by using a multimethod which includes TFIDF, T-VSM, and MDS. The main issue of public debate and the inconsistency level between participants' utterance could be described by using the method. The methodology presented in this study is applied to a case example. Finally, the applicability of the proposed methodology to practical debates is discussed.