To reduce the degree of influence of differential pressure on a pilot valve of a constant flow rate expansion valve. The constant flow rate expansion valve comprises a restriction passage for restricting the flow rate of refrigerant introduced from a refrigerant inlet port, a main valve for controlling the flow rate of refrigerant having flowed out from the restriction passage for discharging the refrigerant to a refrigerant outlet port, a piston for actuating the main valve in the valve-opening/closing direction by the differential pressure between intermediate pressure on the inlet port side of the main valve and pressure in a pressure chamber formed on the opposite side of the main valve, and a pilot valve for sensing the differential pressure proportional to the flow rate of refrigerant flowing through the restriction passage, thereby controlling the pressure in the pressure chamber set by a solenoid. In parallel with the main valve are arranged the pilot valve, the pressure chamber, and a fixed orifice in series in the direction of flow of refrigerant. This makes it possible to apply only the same level of differential pressure as that of small differential pressure applied to opposite end faces of the piston to the pilot valve, thereby making it possible to lessen the degree of influence of differential pressure on the pilot valve.