The purpose of this study is to abstract the feature of the centralized architectural plan of Leonardo da Vinci and to find its
contribution to the Renaissance period. First of all, his drawings are analysed to derive his unique methodology with its sequence
of 'observation of the architectures in centralized plan → examination on the variations of the centralized plan → systemization
of the drawing method for the centralized plan'. Next, his centralized plan sketch with its methodology is studied to find how it
conducts as an 'object' and how it is seen by a human 'Subject'. And the phenomena which newly appeared in Renaissance
period, and their influence to the Modern meaning of Geometry will be verified. Finally, in the last chapter, its contribution to the
Renaissance period is discussed.