To provide a thermostatic refrigerant expansion valve capable of preventing hunting by an expansion valve for causing hunting even by suppressing a cost by discarding a heat insulation layer or covering a temperature sensitive rod with the insulation layer.

A protrusion and recess portion is provided on a contact surface of a temperature sensitive rod 17 with a diaphragm 19, and a partial heat insulation space S is provided to the diaphragm at the rod 17. A heat transfer from the rod 17 to the diaphragm is delayed by the space S. Meanwhile, the rod 17 is covered with a heat insulation layer 33 to delay a temperature transfer from an outlet refrigerant of an evaporator 5 to the rod 17. Thus, even in the case of adopting a variable displacement compressor 1, hunting can be suppressed by delay effects of both the layer 33 and the space S.