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 (24, 24) 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 (24, 24) 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.