A seat for a vehicle, comprising: a seat cushion frame adapted to be moved in a reciprocating manner between a seating position and a retracted position and to support a seat cushion ; a seat back frame adapted to be rotated between a standing position and a forward-tilted position and to support a seat back ; a head rest supported at an upper end portion of the seat back frame and movable between a stationary position and a retracted position; a pair of links provided at both end portions of the seat cushion frame in a lateral direction of the vehicle, one end of each link being adapted to be pivotably connected to a vehicle floor and the other end of each link being connected to a front portion of the seat cushion frame ; a guide member arranged at the vehicle floor and including a guide groove formed to extend between the seating position and the retracted position of the seat cushion frame ; a slide member arranged at a rear end portion of the seat cushion frame and slidably engaging with the guide groove ; a head rest retaining device configured to retain the head rest in the stationary position; a rotary member rotatably supported by the seat back frame and configured to be rotated by the slide member sliding along the guide groove of the guide member ; and an interlocking device arranged between the rotary member and the head rest retaining device and configured to release the head rest from the stationary position in accordance with a rotation of the rotary member , the head rest being retained in the stationary position by the head rest retaining device , wherein the interlocking device is configured to allow the head rest to tilt in the longitudinal direction of the vehicle in conjunction with movement of the seat cushion . a seat cushion frame adapted to be moved in a reciprocating manner between a seating position and a retracted position and to support a seat cushion ; a seat back frame adapted to be rotated between a standing position and a forward-tilted position and to support a seat back ; a head rest supported at an upper end portion of the seat back frame and movable between a stationary position and a retracted position; a pair of links provided at both end portions of the seat cushion frame in a lateral direction of the vehicle, one end of each link being adapted to be pivotably connected to a vehicle floor and the other end of each link being connected to a front portion of the seat cushion frame ; a guide member arranged at the vehicle floor and including a guide groove formed to extend between the seating position and the retracted position of the seat cushion frame ; a slide member arranged at a rear end portion of the seat cushion frame and slidably engaging with the guide groove ; a head rest retaining device configured to retain the head rest in the stationary position; a rotary member rotatably supported by the seat back frame and configured to be rotated by the slide member sliding along the guide groove of the guide member ; and an interlocking device arranged between the rotary member and the head rest retaining device and configured to release the head rest from the stationary position in accordance with a rotation of the rotary member , the head rest being retained in the stationary position by the head rest retaining device , wherein the interlocking device is configured to allow the head rest to tilt in the longitudinal direction of the vehicle in conjunction with movement of the seat cushion . <EOS>