To prevent the drop of result coefficient COP, by checking the occurrence of wet vapor suction phenomena, and suppressing the increase of power consumption of a compressor.

This expansion valve has a steam pressure detection means 21 consisting of the first temperature sensitive tube 210 installed at the inlet of an evaporator 13, and a degree-of-superheating detection means 22 consisting of the second temperature sensitive tube 220 for detection of overheating attached to a refrigerant duct leading to a compressor 10 from the evaporator 13. Then, this decides the opening of a needle valve 23, making use of the pressure difference between the evaporation pressure that the first temperature sensitive tube 210 of the evaporation pressure detection means 21, working within an expansion valve with the response delay of roughly equal orders, and the internal pressure of the second temperature sensitive tube 210 for sensation of the degree of superheating.