An object of the present invention is to provide a thermoelectric conversion element that can demonstrate satisfactory thermoelectric conversion performance, and also has flexibility or can be mounted on a surface having irregularities or a curved surface, a method of manufacturing such a thermoelectric conversion element, and a method of using such a thermoelectric conversion element. A thermoelectric conversion element according to the present invention includes a columnar crystal ferrite layer and an electromotive film formed on the columnar crystal ferrite layer. The electromotive film is configured to generate an electromotive force in an in-plane direction by an inverse spin Hall effect. Columnar crystal grains of the columnar crystal ferrite layer include a major axis a of not less than 200 nm and a minor axis b of not more than 500 nm where a>b.