A straightening device for a vehicle comprising: a main body portion provided in front of a wheel with respect to a forward direction of a vehicle at a lower portion of the vehicle, and being protruded downward with respect to the vehicle from an underfloor; a front straightening portion being formed at a front portion of the main body portion, the front straightening portion being configured to straighten a traveling wind hitting the front portion toward a center side of the front portion in a width direction of the vehicle, and cause the traveling wind to flow out downward with respect to the vehicle, wherein a central portion of the front straightening portion in the width direction of the vehicle is a front inclined surface, which is inclined backward with respect to the vehicle, with a decrease in the distance to a lower side of the vehicle in a lateral view, and both lateral portions of the front straightening portion in the width direction of the vehicle are front lateral surfaces, which extend forward with respect to the vehicle from both end portions of the front inclined surface in the width direction of the vehicle, the straigntening device being characterized in that it further comprises: a rear straightening portion being formed at a rear portion of the main body portion, wherein the rear straightening portion is configured to include a rear inclined surface, and the rear inclined surface is arranged behind the front inclined surface with respect to the vehicle, and the rear inclined surface is inclined backward with respect to the vehicle with decrease in distance to an upper side of the vehicle in a lateral view. a main body portion provided in front of a wheel with respect to a forward direction of a vehicle at a lower portion of the vehicle, and being protruded downward with respect to the vehicle from an underfloor; a front straightening portion being formed at a front portion of the main body portion, the front straightening portion being configured to straighten a traveling wind hitting the front portion toward a center side of the front portion in a width direction of the vehicle, and cause the traveling wind to flow out downward with respect to the vehicle, wherein a central portion of the front straightening portion in the width direction of the vehicle is a front inclined surface, which is inclined backward with respect to the vehicle, with a decrease in the distance to a lower side of the vehicle in a lateral view, and both lateral portions of the front straightening portion in the width direction of the vehicle are front lateral surfaces, which extend forward with respect to the vehicle from both end portions of the front inclined surface in the width direction of the vehicle, the straigntening device being characterized in that it further comprises: a rear straightening portion being formed at a rear portion of the main body portion, wherein the rear straightening portion is configured to include a rear inclined surface, and the rear inclined surface is arranged behind the front inclined surface with respect to the vehicle, and the rear inclined surface is inclined backward with respect to the vehicle with decrease in distance to an upper side of the vehicle in a lateral view. a rear straightening portion being formed at a rear portion of the main body portion, wherein the rear straightening portion is configured to include a rear inclined surface, and the rear inclined surface is arranged behind the front inclined surface with respect to the vehicle, and the rear inclined surface is inclined backward with respect to the vehicle with decrease in distance to an upper side of the vehicle in a lateral view.