An alighting assistance device D of the present disclosure may be a device moving a driver seat rearward in a case where a determination is made that an occupant seated on the driver seat of a vehicle alights. The device may include a reclining mechanism as one example of an angle changer which changes an angle of a seat back of the driver seat with respect to a horizontal plane, a sitting height acquirer which acquires a sitting height of the occupant, and a seat controller as one example of an angle controller which controls the angle changer such that the angle of the seat back becomes closer to be perpendicular as the sitting height acquired by the sitting height acquirer is higher in the case where a determination is made that the occupant alights.