HEADREST DEVICE

PROBLEM TO BE SOLVED: To predict whether being brought into collision from the rear, without the use of detection means such as a radar to detect following vehicles, and properly determine a size of the back-set between a head of an occupant and a headrest according to prediction results.SOLUTION: A headrest device includes means for: detecting the position of a vehicle and speed; acquiring information showing the speed and position of a following vehicle from the following vehicle by a vehicle-to-vehicle communication; and controlling the movement of the position of a headrest front part 12b so that the back-set is reduced in comparison with the back-set that is a distance between a head of an occupant A and the headrest front part 12b in the horizontal direction in the case where the distance is longer than a predetermined distance or the speed of the vehicle is higher than the speed of the following vehicle, when a distance between the vehicle and the following vehicle, which is determined from the position of the vehicle and the position of the following vehicle, is a predetermined distance or less, and the speed of the vehicle is slower than the speed of the following vehicle (S114).