Headrest device

A headrest device comprises a headrest body which includes a headrest rear portion supported with respect to a seatback of a seat on which a passenger of a vehicle sits, and a headrest front portion that is movable within a predetermined range from a fully closed position that is closest to the headrest rear portion to a fully open position that is farthest from the headrest rear portion; a detection unit which detects a running state or an operation state of the vehicle; a prediction unit which predicts a possibility of a rear vehicle collision with the vehicle on the basis of the running state or the operation state of the vehicle detected by detection unit; and a control unit which controls, in a case in which the possibility of the rear vehicle collision is predicted by the prediction unit, movement of a position of the headrest front portion so that a backset becomes smaller than a backset at the time of the prediction, the backset being a horizontal distance between the headrest front portion and a head of the vehicle passenger.