A more comfortable seat is provided by detecting whether or not a person is in a seat. A seat has a heating element 1, a seat surface temperature detector 5 that is situated below a seat surface cover and that detects the temperature of the seat surface, and a seating determination unit 6 for determining whether or not a seat is occupied. A determination is made as to whether or not a seat is occupied according to an amount of temperature change detected by the seat surface temperature detector 5 for a predetermined period of time, whereby a determination can be readily made as to whether or not a person is seated. When no one is seated, application of power to the heating element 1 is stopped, and the like, which in turn contributes to energy saving and enhancement of fuel efficiency.