A thermoelectric power generation device comprising: a first power generation module and a second power generation module which are in contact with opposed outside surfaces of the duct respectively to clamp the duct therebetween and each of which includes therein a thermoelectric power generation element; a first outside plate and a second outside plate each of which is in contact with an outside surface of a corresponding one of the first power generation module and the second power generation module on its opposite side from the duct; and outside fins (5, 6) each of which is provided on an outside surface of a corresponding one of the first outside plate and the second outside plate on its opposite side from a corresponding one of the first power generation module and the second power generation module, wherein: each of the first outside plate and the second outside plate includes bent portions (3a, 4a) at its both ends in a direction perpendicular to a direction in which the low-temperature fluid flows; characterized by a duct in which a low-temperature fluid flows; the outside fins (5, 6) being in contact with a high-temperature fluid; the bent portions of the first outside plate and the bent portions of the second outside plate being respectively welded together in a resiliently deformed state to approach each other; each of the outside fins (5, 6) including a plurality of wave portions; the bent portions of the first outside plate and the bent portions of the second outside plate being perpendicular to a direction in which the high-temperature fluid flows; and the bent portions of the first outside plate and the bent portions of the second outside plate being respectively welded together to generate stress that presses the first power generation module and the second power generation module on the duct. a first power generation module and a second power generation module which are in contact with opposed outside surfaces of the duct respectively to clamp the duct therebetween and each of which includes therein a thermoelectric power generation element; a first outside plate and a second outside plate each of which is in contact with an outside surface of a corresponding one of the first power generation module and the second power generation module on its opposite side from the duct; and outside fins (5, 6) each of which is provided on an outside surface of a corresponding one of the first outside plate and the second outside plate on its opposite side from a corresponding one of the first power generation module and the second power generation module, wherein: each of the first outside plate and the second outside plate includes bent portions (3a, 4a) at its both ends in a direction perpendicular to a direction in which the low-temperature fluid flows; characterized by a duct in which a low-temperature fluid flows; the outside fins (5, 6) being in contact with a high-temperature fluid; the bent portions of the first outside plate and the bent portions of the second outside plate being respectively welded together in a resiliently deformed state to approach each other; each of the outside fins (5, 6) including a plurality of wave portions; the bent portions of the first outside plate and the bent portions of the second outside plate being perpendicular to a direction in which the high-temperature fluid flows; and the bent portions of the first outside plate and the bent portions of the second outside plate being respectively welded together to generate stress that presses the first power generation module and the second power generation module on the duct. each of the first outside plate and the second outside plate includes bent portions (3a, 4a) at its both ends in a direction perpendicular to a direction in which the low-temperature fluid flows; characterized by a duct in which a low-temperature fluid flows; the outside fins (5, 6) being in contact with a high-temperature fluid; the bent portions of the first outside plate and the bent portions of the second outside plate being respectively welded together in a resiliently deformed state to approach each other; each of the outside fins (5, 6) including a plurality of wave portions; the bent portions of the first outside plate and the bent portions of the second outside plate being perpendicular to a direction in which the high-temperature fluid flows; and the bent portions of the first outside plate and the bent portions of the second outside plate being respectively welded together to generate stress that presses the first power generation module and the second power generation module on the duct.