It is highly important in Japan to choose a good site for wind turbines, because the spatial distribution of wind speed is quite complicated over steep complex terrain. We have been developing the unsteady numerical model called the RIAM-COMPACT【○!R】 (Research Institute for Applied Mechanics, Kyushu University, COMputational Prediction of Airflow over Complex Terrain). The RIAM-COMPACT【○!R】 is based on the LES (Large-Eddy Simulation). The object domain of the RIAM-COMPACT【○!R】 is from several m to several km, and can predict the airflow and gas diffusion over complex terrain with high precision. In the present paper, the designed wind speed evaluation technique in WTG (Wind-Turbine Generator) installation point by using the MM5 mesoscale meteorological model and RIAM-COMPACT【○!R】 CFD model was proposed.