A thermoelectric conversion device includes thermoelectric layers and connection layers that are alternately provided in a first direction parallel to surfaces of the thermoelectric layers, and are connected to each other, thermally conductive layers that are connected to the respective connection layers, and extends in a second direction intersecting the surfaces, a first insulating layer that has a smaller thermal conductivity than the thermally conductive layers, and a second insulating layer that has a smaller thermal conductivity than the first insulating layer, is provided between the first insulating layer and the thermoelectric layers, and has a thickness equal to or greater than ¼ of a distance between an end of the thermally conductive layer at a side of one of the thermoelectric layers and a center of another of the connection layers in the first direction, the thermally conductive layers penetrating through the first and second insulating layers.