As a wrist portion of an application robot equipped with a plurality of application nozzles moves in a predetermined operation pattern, viscous damping and constraining materials having different properties are simultaneously injected from the application nozzles so that immediately after the damping material is injected from the preceding application nozzle, as viewed in the moving direction and applied to a vehicle body panel as an underlayer material, the constraining material having different property is injected from the succeeding application nozzle, as viewed in the moving direction, and applied as an overlayer material over the underlayer material.