The utility model discloses a seat headrest comprising a main headrest body, a left champing block and a right champing block, wherein the main headrest body is provided with a horizontal positioningbox, a left stay bar and a right stay bar, a horizontal slide chute inside the horizontal positioning box is internally provided with a left rack and a right rack which can relatively horizontally slide, a gear is arranged between the left rack and the right rack, the left rack and the right rack are provided with horizontal teeth which are mutually matched and are meshed with the gear, and the middle of the gear is provide with a positioning shaft; the left champing block is fixed at the left side of the left rack; the right champing block is fixed at the right side of the right rack; the endpart of the left stay bar passes through the left champing block and then is arranged in the horizontal positioning box, and the end part of the right stay bar passes through the right champing blockand then is arranged in the horizontal positioning box. The utility model has the advantages of simple structure, accurate positioning, convenient installation and use, small occupying transportationspace, and the like; and in addition, the seat headrest can be widely used for seats inside an automobile, a theater, a council chamber, a cruise ship, a plane, a house, other amusement places, and the like.