An air guiding device for a motor vehicle, in particular a rear spoiler, can be moved between a retracted non-use position and at least one deployed use position and contains an air guiding body on which are disposed two lateral air guiding body sections which can be moved in the vehicle transverse direction. Here, it is important that, in the non-use position of the air guiding device, the lateral air guiding body sections form a common joint which runs in the vehicle longitudinal direction, with at least one of the two air guiding body sections having, on its side which forms an edge of the common joint, a depression at least in regions.