To obtain a pyroelectric infrared thin-film element which prevents a mechanical stress from being generated in an infrared detection part by a method wherein an upper-part electrode and a lower-part electrode are formed respectively of a material whose coefficient of linear expansion is close to the coefficient of linear expansion of a pyroelectric thin film.

A Pt film as a lower-part electrode 5 is formed on the surface of a single-crystal substrate 1 by a sputtering operation. A PZT-based ferromagnetic thin film as a pyroelectric film 3 is formed on the surface of the lower-part electrode 5 by a MOSCVD (a metal organic chemical vapor deposition method). A Pt film as an upper-part electrode 4 is formed on the surface of the pyroelectric thin film 3 by a sputtering operation. The upper-part electrode 4 and the lower-part electrode 5 which constitute an infrared detection part 6 are formed of the same material so as to be the same film thickness. The difference between the coefficient of linear expansion of Pt as the material for the electrodes and the coefficient of linear expansion of the pyroelectric thin film 3 sandwiched between the upper-part electrode 4 and the lower-part electrode 5 is reduced. That is to say, in a thin-film element S, the upper-part electrode 4 and the lower-part electrode 5 are formed of the same material so as to be the same thickness, and the coefficient of linear expansion of the material is made similar to that of the thin film 3.