A rear spoiler device (10) for a vehicle (1) has at least one rear door (8, 9), wherein the rear spoiler device (10) has at least one side spoiler (16, 17) with at least one side air guide element (32), which can be moved between a driving position for contour extension and aerodynamic air guidance when the rear door (8, 9) is closed, and a base position when the rear door (8, 9) is open. The side spoiler (16, 17) furthermore has a swing arm (30) with a first pivot joint (31) for pivotable fixation to the rear door (8, 9), the side air guide element (32) is mounted pivotably on the swing arm (30) via at least one second pivot joint (34), and the side air guide element (32) has a locking arrangement on its front end region (32a) for releasable and lockable fixation to the truck (1).