This paper describes the results of our experimental and numerical analysis of the effect of ventilation on the change of air contaminant in the vehicle passenger compartment. Until recently there have been only a few studies of vehicle passenger compartment ventilation. None of them have been considered the interior configuration, fresh air inlet conditions, interior air outlet condition, etc. which are factors determining the ventilation capacity.To achieve this we experimented, using a 2-dimensional 1/5 scale model, as to how interior air can be exchanged with fresh air by changing inlet velocities, outlet positions, etc. In order to compare relatively with previous experimental results, moreover, we performed numerical analysis, applying a Finite Element Method.According to this study, experimental results and numerical ones were qualitatively consistent. From both results it has been found that the interior air contaminant concentration is strongly affected by the interior flow pattern. This numerical analysis is a useful means of evaluating ventilation capacity in the initial stage of the vehicle passenger compartment design.