The purpose of this thesis is to examine Buddha`s silence, i.e. Avyakatavada based on Lankavatarasutra, the Mahayana Sutras, and to examine Avyakatavada focusing on Buddha`s dialogic method which is based on Daegi Buddhist sermon. Buddha`s dialogic method is an important element for Daegi Buddhist sermon according to the level of the other party of dialogue. Buddha draws the questioner`s inner change by making the questioner the principal agent proceeding with dialogue and realizing personally, rather than providing the questioner with the knowledge unilaterally in the course of dialogue. In order to maintain this dialogic method with the questioner as the principal agent, Buddha answers to the questions in four ways according to the questioner`s spiritual level. Of these four answering methods, it is Banmoon, meaning asking in return, and Jigi, meaning silence that reveals the characteristics of Buddha`s dialogic method best. First, Buddha`s Banmoon is the method used for Buddhists. This is a unique method in which Buddha makes the questioner the principal agent and become the agent of self-awareness. Buddha induces the questioner to be self-aware of inverted cognition through Banmoon. Accordingly, Banmoon in Buddha`s dialogic methods is Buddha`s unique way of salvation so that the questioners can be led to nirvana by cultivating autonomous capabilities to solve problems personally through meditating their questions. Second, Buddha`s Avyakatavada is Buddha`s method of answering non- Buddhists` metaphysical questions. Lankavatarasutra`s answer to the question, ``Why did Buddha keep silent" is that it was because Buddha considered that non-Buddhists`` metaphysical questions were not right questions. And it says that the reason that they are not right questions is that the questions are asked when the questioners` spiritual level is not mature enough to be equipped with right cognition. So the meaning of Avyakatavada in Lankavatarasutra is interpreted as ``not explained." Lankavatarasutra says that in order to be a right question, the questioner should be equipped with right cognition and it should begin with realizing that all created things appear in one`s mind and getting rid of wrong opinions about the Creator creating all things. So Avyakatavada is interpreted as Chidap (置答) since the answer is temporarily reserved until the questioner is equipped with right cognition about Citta-Matra. Accordingly, Buddha`s silence can be regarded as Buddha`s Banmoon toward non-Buddhists, and it is ``altruistic silence`` waiting for non-Buddhists` spiritual level to be mature enough to solve problems personally by continuously thinking about their questions through Banmoon which is silence. Thus, this thesis newly established the meaning of silence of the question, ``Why did Buddha keep silent?`` by examining the meaning of Buddha`s silence in Lankavatarasutra, i.e. Avyakatavada within the framework of Daegi Buddhist sermon, which is characteristics of Buddha`s sermon methods, and Buddha`s dialogic method.