A thermoelectric conversion element includes a magnetic layer which has a component magnetized in an in-plane direction, an electromotive layer which includes a material with spin orbit coupling, and a spin injection layer. The spin injection layer is provided between the magnetic layer and the electromotive layer and magnetically coupled to both the magnetic layer and the electromotive layer. A magnetic moment per unit volume of the spin injection layer is smaller than the magnetic moment per unit volume of the magnetic layer.