In the paper, wind inflows to a building group affected by strong winds in urban area and wind outflows from the building group are computed by computational fluid dynamics analysis. For eight wind directions, flow rates at inlet and exit areas are computed based on the computed inflows and outflows. Also, the ratio of flow rates, which is the ratio of flow rate at exit area to that at inlet area, is evaluated according to the rate of building area to inlet area, and the effects that the wind directions and the rate of building area to inlet area have on the ratio of flow rates are investigated. It was found in the study that due to buildings, velocities at most points in the area of the building group decreased. It was also shown that the ratio of flow rates ranged from approximately 5.8% to 28.9% for the eight wind directions, and that generally the less the rate of building area to inlet area, the larger the ratio of flow rates.