One aspect of the present invention includes a thermoelectric conversion unit having a case in which a flow path of an open structure is molded, a first substrate covering an open portion of the flow path, a second substrate arranged opposite the first substrate, and a plurality of thermoelectric conversion elements arranged between the first substrate and the second substrate. At a bottom surface of the flow path of the case, an introduction pipe and a discharge pipe are formed integrally with the case, and each of the introduction and discharge pipes extend in a direction perpendicular to the first substrate.