PURPOSE:To obtain a small-sized, low-cost sensor by covering a sending film for reference with a shield body without using a can package for hermetic sealing. CONSTITUTION:An SiO2 film 2 on an Si substrate is etched anisotropically to form a couple of through grooves and a bridge 3 is provided between the grooves. The sensing film 4 made of a thin film thermistor material is provided on the bridge 3 and a couple of inter-digital electrodes for impedance detection are provided on the film 4. Two bridges 3 are provided successively on the substrate and the same sensing film 5 is mounted on the other bridge 3. The sensing film 4 is exposed to the external field and varies in impedance with temperature. The shield body 6 provided with a cubic Si block recessed part is adhered on the substrate 1 mounted on the sensing film 5 and sealed airtightly so that it is not affected by the humidity of the external field. Both sensing films 4 and 5 vary similarly with atmospheric temperature, so temperature compensation is performed and the humidity of the external field is accurately detected from the output difference between the outputs of both films 4 and 5.