Abstract: The water closet seat is provided with long holes for blowing hot air, and the hot air is blown to the long holes by means of an air heater which heats air and supplys hot air to heat the closet seat for a short time or to keep the closet seat warm, and the water closet seat is provided with offensive odor guiding long holes and is provided with a plurality of offensive odor suction ports which are directed from the long holes for guiding offensive odor towards the water closet seat, and the offensive odor is sucked into the offensive odor guiding long holes at a close distance from the filth by means of the suction force of a ventilator, and the hot air blowing long holes and offensive odor guiding long holes are mutually communicated and the offensive odor and the used hot air passing through the hot air blowing long holes are exhausted outside by means of the ventilator, and thus objects of keeping the closet seat warm and of exhausting the offensive odor in the lavatory can be achieved.