It is one object of the present invention to provide a control for moving a head rest in response to a signal from a sensor detecting a distance between the head rest and a head of a passenger, in which even if the head of the passenger moves within a predetermined range, the head rest can be prevented from moving depending on the motion of the head of the passenger so as to remove discomfort for the passenger.Therefore, the present invention has a construction as follows.A head rest control system in which a head rest of a seat of a vehicle is constructed to be moved back and forth by a head rest moving mechanism may include a sensor detecting a distance between the head rest and a head of a passenger, and a control device controllably actuating the head rest moving mechanism. The control device is constructed to actuate the head rest moving mechanism when the distance between the head rest and the head detected by the sensor is outside of a proper range of clearance in which it is possible to deal with a back-side collision of the vehicle, thereby moving the head rest to a proper position in which it is possible to deal with the back-side collision of the vehicle.