To provide a vehicular drag reducing device which reduces drag working on a vehicle at drive time.

The vehicular drag reducing device 20 is equipped with the cargo box front (forward surface) 13 facing the front of a vehicle which is mounted on the outside of the forwardly movable vehicle and with the movable plate top surface (vestibular surface) 31a extending in the longitudinal direction D1 of the vehicle toward the front from the base end of the cargo box front 13. The cargo box front 13 is the vehicular drag reducing device 20 arranged so as to be orthogonal to the movable plate top surface 31a and to the longitudinal direction D1 of the vehicle.