Aerodynamic effects on the windshield wiper system are investigated numerically in this study. The drag coefficient and the lift coefficient are examined as a function of the shape and dimension of wiper-arm and wiper-blade, the distance between wiper-blade and wiper-arm. The calculated results show that the deformation of a wiper-blade affects the lift force only, but the shape and dimension of the wiper-arm and the distance between the wiper-blade and the wiper-arm affect both the drag force and the lift force. To conclude, the height of the wiper-arm and the aperture in the wiper-arm play important roles in the aerodynamic behavior of the wiper.