A power generation apparatus, comprising: a cooling unit; a first thermoelectric module including a first thermoelectric element disposed on a first surface of the cooling unit and a first heat sink disposed on the first thermoelectric element; a second thermoelectric module including a second thermoelectric element disposed on a second surface of the cooling unit and a second heat sink disposed on the second thermoelectric element; a first guide plate disposed to face the first thermoelectric module; a second guide plate disposed to face the second thermoelectric module; a branch unit disposed on a third surface between the first surface and the second surface of the cooling unit; and a separation member disposed on a fourth surface perpendicular to the first surface, the second surface and the third surface of the cooling unit, wherein each of the first heat sink and the second heat sink includes a plurality of heat dissipation fins spaced apart from each other, wherein the cooling unit is a duct through which a first fluid passes, and the branch unit branches a second fluid having a temperature higher than that of the first fluid, and wherein the second fluid passes between the first thermoelectric module and the first guide plate and the second thermoelectric module and the second guide plate wherein a ratio of a shortest horizontal distance between the first heat sink and the first guide plate to a shortest horizontal distance between the branch unit and the first guide plate ranges from 0.0625 to 0.25, a ratio of a shortest horizontal distance between the second heat sink and the second guide plate to a shortest horizontal distance between the branch unit and the second guide plate ranges from 0.0625 to 0.25, the separation member extends from the fourth surface toward the first surface and the second surface, comes into contact with the first surface and the first guide plate, and comes into contact with the second surface and the second guide plate. a cooling unit; a first thermoelectric module including a first thermoelectric element disposed on a first surface of the cooling unit and a first heat sink disposed on the first thermoelectric element; a second thermoelectric module including a second thermoelectric element disposed on a second surface of the cooling unit and a second heat sink disposed on the second thermoelectric element; a first guide plate disposed to face the first thermoelectric module; a second guide plate disposed to face the second thermoelectric module; a branch unit disposed on a third surface between the first surface and the second surface of the cooling unit; and a separation member disposed on a fourth surface perpendicular to the first surface, the second surface and the third surface of the cooling unit, wherein each of the first heat sink and the second heat sink includes a plurality of heat dissipation fins spaced apart from each other, wherein the cooling unit is a duct through which a first fluid passes, and the branch unit branches a second fluid having a temperature higher than that of the first fluid, and wherein the second fluid passes between the first thermoelectric module and the first guide plate and the second thermoelectric module and the second guide plate wherein a ratio of a shortest horizontal distance between the first heat sink and the first guide plate to a shortest horizontal distance between the branch unit and the first guide plate ranges from 0.0625 to 0.25, a ratio of a shortest horizontal distance between the second heat sink and the second guide plate to a shortest horizontal distance between the branch unit and the second guide plate ranges from 0.0625 to 0.25, the separation member extends from the fourth surface toward the first surface and the second surface, comes into contact with the first surface and the first guide plate, and comes into contact with the second surface and the second guide plate.