Abstract: There is provided a pyroelectric infrared sensor being capable of changing its shape and having high sensitivity. The sensor comprises the substrate 11 made of a polymer material such as polyimide or polyethylene terephthalate and having flexibility, the layer 13 comprising vinylidene fluoride (VDF), and the flexible electrodes 12 and 14 comprising an Al-deposited film and provided on and under the VDF oligomer layer 13. The pyroelectric infrared sensor of the present invention has flexibility as a whole due to flexibility of each component elements and can be formed into desired shapes. In addition, since a substrate made of a polymer material has heat capacity and heat conductivity lower than those of Si substrates used on conventional pyroelectric infrared sensors, sensitivity of the sensor can be increased.