To provide a straightening device of an automobile for stably reducing travelling air resistance with a simple structure.

The straightening device includes: a wing-like straightening vane support part 11 having a front side portion 13 which has an upper edge connected to a straightening device mounting part 9 extending on a front portion of a vehicle body in a vehicle width direction and which is vertically expandable in the vehicle width direction and having a lower side portion 14 which is connected to a lower edge of the front side portion 13 and which extends in the vehicle width direction; and a wing-like straightening vane 20 which is connected to the lower side portion 14 of the wing-like straightening vane support part 11 via a plurality of partition walls 18 and which receives a depressive force for pushing down by pressure difference of traveling wind flowing along an upper surface 21 and traveling wind flowing along a lower surface 22. The front side portion 13 of the wing-like straightening vane support part 11 is expanded and contracted by the descent and ascent of the wing-like straightening vane 20.