To provide a vehicular rear bumper structure, which enhances the degree of freedom in design of a rear bumper, while air in the inside of the rear bumper can be sucked by traveling wind and an exhaust performance of a ventilator for removing air inside a vehicle can be improved.

In the vehicular rear bumper structure, the lower end 1K of the rear bumper 1 projects downwardly with respect to the lower end 2K of a rear vehicle body 2 on a front side Fr. A bumper extension 15 provided along the rear bumper 1 is attached to the rear side of the lower end 1K of the rear bumper 1, and the upper end 17 of a transverse center of the bumper extension 15 is downwardly positioned diagonally behind the lower end 2K of the rear vehicle body 2. Air between the rear bumper 1 and the rear vehicle body 2 is removed by traveling wind from between the upper end 17 of the transverse center of the bumper extension 15 and the lower end 2K of the rear vehicle body 2.