The object of the present invention is to provide an expansion valve that suppresses noise generated when an air conditioner is started, and achieves saving of driving force. The stroke of a valve element is set such that refrigerant flows at a flow rate 1.0 to 1.4 times the flow rate corresponding to the set tonnage. This limits the valve lift of the valve in the fully open state during start-up such that it provides a flow rate of refrigerant only 1.0 to 1.4 times the flow rate corresponding to the set tonnage. This prevents an unnecessary and excessive amount of refrigerant from flowing, whereby it is possible to reduce flow noise of refrigerant during start-up. Further, since the excessive amount of flow of refrigerant is reduced, it is possible to achieve saving of driving force.