To restrain generation of both a window slob sound and a wind noise.

This vehicular deflector mechanism is used for a vehicle 11 having a roof 12 forming an opening part 15, and comprises a deflector 16 extending in the vehicle width direction of the vehicle, arranged on the front end 15 of the opening part, having one edge part 25 formed in a projection-recess shape and having the other edge part 27 formed in a flat shape, a support member 17 connecting the deflector to the roof, a first shaft part 18 rotatably connecting one end 17A of the support member to the deflector, and a deflector driving means 28 rotating the deflector around the first shaft part in response to a speed of the vehicle and selectively projecting one edge part or the other edge part upward from the front end of the opening part.