Disclosed are a method for producing a complex oxide film having a high relative dielectric constant, an arbitrarily controlled thickness and low temperature dependency of capacity without requiring a complicated large facility, and such a complex oxide film. Also disclosed are a composite body containing such a complex oxide film, a method for producing such a composite body, a dielectric material or piezoelectric material containing such a complex oxide film or composite body, a capacitor or piezoelectric element containing a complex oxide film having low temperature dependency of capacity, and an electronic device comprising such a capacitor or piezoelectric element. Specifically disclosed is a complex oxide film containing titanium element and calcium element which is obtained by forming a metal oxide layer containing titanium element on a substrate surface by anodizing or the like, and them reacting a solution containing calcium ions with the metal oxide layer. Also specifically disclosed are a capacitor containing a composite body having such a complex oxide film as a dielectric material, and a piezoelectric element containing a composite body having such a complex oxide film as a piezoelectric material.