PURPOSE: To freely adjust the position of a headrest fitted to the backrest of a vehicle seat and improve the supporting strength against the external force at the time of a vehicle collision or the like.

CONSTITUTION: The rotation of a headrest 5 is restricted by a rotation lock mechanism provided between a rotor 11 and a backrest 3. The check balls 9 of a vertical shift lock mechanism provided in the hole 7a of the second bracket are pushed by the front and rear faces of the first bracket 6 and thrust into the hole 7a of the second bracket. The check balls 9 are extruded by the restoring force of a spring 8 to other holes 6a of the first bracket 6 at the lock position, and the check balls 9 are engaged with the holes 6a for height adjustment. An impact load is received by the front face of the second bracket 7, and it is dispersed to the backrest 3 from shaft sections 7b on both sides of the second bracket 7 via the right and left bearing sections 4c of a storage recess 4, and dispersed to the backrest 3 from rotation lock mechanism, thereby the supporting strength against the impact load can be secured.