A thermoelectric generator for a vehicle is mounted at an exhaust pipe and produces electricity using a temperature difference between the exhaust gas and coolant. The generator includes: a housing; thermoelectric modules mounted at an outer circumferential surface of the housing; a plurality of coolant tubes mounted so as to closely attach the thermoelectric module to the housing; first coolant containers mounted at both ends of the coolant tubes, respectively; and second coolant containers mounted at both ends of the coolant tubes, respectively. The coolant tubes are assembled to the first and second coolant containers as a modularized type, and thus assemblability may be improved and partial replacement of components in case of breakdown may be easily performed. In the coolant tube of the present invention, heat exchange is concentratedly performed at a portion in contact with the thermoelectric module, and thus generation efficiency may be more improved.