To provide a heat converter for condensation that can be miniaturized and reduced in weight and can promote miniaturization, cost reduction and energy saving of a refrigeration system using the heat converter to thereby contribute to global environment conservation, and a refrigeration system using the heat converter.A heat converter 30 for condensation which changes high-temperature and high-pressure refrigerant gas discharged from a compressor 1 of a refrigeration system to low-temperature refrigerant liquid is constructed by a isobaric cooling unit 3 for cooling the high-temperature and high-pressure refrigerant gas under isobaric change, a pressure-reducing liquefying unit 6 for liquefying gas refrigerant partially-liquefied in the isobaric cooling unit by a refrigerant acceleration phenomenon while the pressure and enthalpy are reduced, and a pressure-reducing and cooling unit 8 for cooling the refrigerant passed through the pressure-reducing and liquefying unit by the refrigerant acceleration phenomenon while the pressure and enthalpy are reduced.