Spoiler device for a motor vehicle

Air guiding device of a motor vehicle, comprising a spoiler (12-12d), which is adjustable by means of an adjustment device between a rest shape, in which it lies substantially within the vehicle contour, and an operation form in which it extends beyond the vehicle contour, wherein the spoiler (12 -12D) has a spoiler surface (at least in the operating mode of the spoiler 12-12d) is flown by the airstream during travel of the motor vehicle and thereby is aerodynamically effective, characterized in that the spoiler (12-12d) (a spoiler body 14 has 14d) and arranged at both lateral ends of the spoiler body spoiler extensions (18-18c) whose position relative to the spoiler body (14-14d) over the course of the displacement from the rest form for operating form in the sense of increasing the aerodynamic spoiler surface to increase the aerodynamic effectively changed.