A thermoelectric conversion element is made of an alloy including a transition metal. The alloy is a compound having a crystal structure including a Kagome lattice plane constituted by the transition metal, and exhibits an anomalous Nernst effect. A thermoelectric conversion device includes a substrate and a plurality of thermoelectric conversion elements on the substrate. Each of the plurality of thermoelectric conversion elements is defined as the thermoelectric conversion element described above and has a shape extending in one direction. The plurality of thermoelectric conversion elements are arranged in parallel in a direction perpendicular to the one direction and electrically connected in series.