Rapid urban development has significantly changed the regional climate and caused various environmental problems such as heat island. Air temperature increase in Tokyo during the past hundred years is much more rapid than the global air temperature rising. It is important to clarify the effects of urbanization on climatic change for adequate urban planning. Numerical model is expected a powerful tool which can estimate the effects of urbanization on climatic change. The model for geophysical flow problems developed by Mellor and Yamada is used for turbulence closure. The results of CFD (Computational Fluid Dynamics) analyses of mesoscale climate in the Tokyo area are presented. In this paper, five cases of computations are carried out in order to examine the influences of climatic change about effects of land-use conditions with urban development. We investigate temperature fields and velocity fields as buildings area and paved road area is changed to forest or grass, etc. Futhermore, climatic change from the end of the Japanese Medieval Period (Edo period, around 1830s) to the present is analyzed. By comparing the results of these analyses, the effects of urbanization on the heat island in the Tokyo area are clarified.