The headrest, which is provided on a seat back of a seat comprises a pair of spaced support brackets fixed within the seat back. A shaft is rotatably extended between the pair of support brackets. The shaft is provided with a sprocket. A headrest body is fixed via a stay to the shaft. A motor is fixed in the seat back. The motor is disposed at a lower part of a lateral side of the seat back and has a second sprocket. An endless chain is extended between the sprockets. An operation of the motor causes cyclic movement of the endless chain to rotate the shaft, thereby displacing the headrest body in a direction forwardly and backwardly relative to the seat back.
