In an undercover structure according to the present invention, a first cover part that is a lowermost part of an undercover has a first rear end positioned ahead of a front wheel axle. Further, a curved part with a predetermined curvature is formed at the first rear end of the first cover part in a side view. This generates a strong negative pressure in a region ahead of the front wheel axle 21. Accordingly, the flow rate of air flowing to each wheelhouse 23 decreases (the flow rate of the airflow between a road and a vehicle generated along the bottom surface of the first cover part 15a of the undercover 15 increases). This causes an attraction force that attracts the vehicle to a road surface to act on a vehicle body of the vehicle, thereby making traveling stability more excellent.