PURPOSE: To prevent a metal powder etc. from mixing into a refrigerant by constituting the valve mouth of a valve of a metal material, of which the Vickers hardness is specified.

CONSTITUTION: An expansion valve is constituted by combining an orifice member 100 on an orifice 30. The orifice member 100 is made of a metal material of which the hardness is higher compared with the material of a valve main body 10. The material is a metal material of which Vickers hardness is 150-500, e.g. when the valve main body 10 is made of brass, the orifice member 100 is formed of a stainless steel. A valve body 9 is also formed of stainless steel, etc. In order to combine the orifice member 100 to the valve body 10, press fitting can be used. The combining can be made even more secure by forming a tapered protruding end at the leading end of the orifice member 100 in the press fitting direction. By making a valve seat of a stainless steel, a corrosion due to erosion can be prevented from happening.