Abstract: An evaporator using a CO2 refrigeration that prevents a raise in vapor quality of refrigeration in an evaporator passage to obtain heat exchanging efficiency. The evaporator for use in a refrigeration system includes a refrigerant inlet for introducing a refrigerant, a refrigerant outlet for discharging the refrigerant, and an evaporator passage for causing the refrigerant introduced via the refrigerant inlet to evaporate and leading the refrigerant to the refrigerant outlet. An intermediate outlet is provided at an intermediate portion of the evaporator passage. A refrigerant high in vapor quality among the refrigerant passing through the intermediate portion from the refrigerant inlet flows out of the intermediate outlet to prevent a raise in vapor quality of refrigerant.