PURPOSE: To make a ventilation fully operated in around the foot of rear seat, with a good air circulation as well in the seat, by providing a forced ventilator in the bottom portion of the set, and forcibly ventilating the seat or around the foot of the rear seat.

CONSTITUTION: In the puncheon of a seat S, are perforated many vent holes 7 linked to an air box 1 through a link port 12, and an opening is provided of a ventilation port 10, to which a reversibly rotatably fan 2 is installed, in a rear wall 9 of the box 1, and of a suction port 11 in a front wall 8, respectively. On a day at high temperature, air in around the foot of rear seat is sucked into the box 1 from the ventilation port 10, and delivered out of a trim cover 6 passing through from the link port 12 to the vent hole 7 and the first cushion material 5a, and on a day at low temperature, a selector door 13 is rotated, and the suction port 11 and the ventilation port 10 are linked, with the link port 12 closed. In this way, a wind, blown out to around the foot of the front seat from the room heater, is sucked into the box 1 from the suction port 11, and blown out to around the foot of the rear seat from the ventilation port 10.