A pressure sensor in the form of film is provided, for instance, between the surface of a vehicle seat and a cushion material such as urethane. A sensor (20) in the form of film comprises an insulating film (21a, 21b), on which is formed a temperature detector (25) for detecting the temperature of a pressure detector (23). The temperature detector (25) is composed of a material whose electrical resistance varies with temperature. The temperature measured by the temperature detector (25) is used to reduce or eliminate measurement errors caused by varying temperature.