and the low pressure chamber 11 that are collectively called the refrigerant passage the high pressure chamber 10 will be referred to as a first chamber which has an inlet pressure relatively higher when the refrigeration cycle is operated the low pressure chamber 11 will be referred to as a second chamber which has a specific pressure lower than the inlet pressure when the refrigeration cycle is operated the valve casing 1 has an additional passage 15 communicating the low pressure chamber 10 with the particular chamber 14 through a through hole 204a of the adjustment screw 204 the additional passage 15 is for introducing the specific pressure into the particular chamber 14 as a result of being introduced with the specific pressure the particular chamber 14 has particular pressure relating to the specific pressure the expansion valve unit 2 has a first partitioning wall 21 formed between the high and the low pressure chambers 10 and 11 the valve seat 200a is formed on the first partitioning wall 21 to project in the high pressure chamber 10 a combination of the first partitioning wall 21 and the valve seat 200a defines the port 200b connecting the high pressure chamber 10 with the low pressure chamber 11 the valve body 201 faces.