To provide a device for obtaining the stability of a head part to sidewise sways due to a centrifugal force caused at the time of running to make a right or left turn and running to make a curve during the running of a car and buffering effects to impacts by using a mounting rod of a car seat headrest and passing the car seat headrest mounting rod through a hole provided in a base to mount and secure it.

A hole, through which a car seat headrest mounting rod is passed, is provided in a base (3) and arms (2) having the main bodies of guards (1) integrally therewith on both sides of the base are mounted to both sides of the base. A car seat headrest is removed, and the car seat headrest mounting rod is mounted to a car seat while being passed through the hole provided in the base again.