Disclosed is a power generation device including a case including a through hole configured to pass therethrough in a first direction and form an inner surface, a duct disposed in the through hole of the case and having a flow path such that a first fluid flows in a second direction perpendicular to the first direction, a first thermoelectric module including a first thermoelectric device disposed on a first surface of the duct and a first fin disposed in the first thermoelectric device, a second thermoelectric module including a second thermoelectric device disposed on a second surface facing the first surface of the duct and a second fin disposed in the second thermoelectric device, a plurality of first guide portions coupled to the case and disposed on the duct while facing each other, and a second guide portion disposed on a third surface formed between the first surface and the second surface of the duct. Here, the second guide portion extends between the plurality of first guide portions in the second direction. Also, the plurality of first guide portions and the second guide portion each include a tilting surface, and a tilt angle of the tilting surface of the second guide portion differs from a tilt angle of the tilting surface of each of the plurality of first guide portions.