A drive control device performs a mode change with a constant current between a first mode in which an opening degree of a refrigerant passage is changed in a first flow region where a flow rate of refrigerant flowing through the refrigerant passage is lower than or equal to a predetermined value and a second mode in which the opening degree of the refrigerant passage is changed in a second flow region where the flow rate of refrigerant flowing through the refrigerant passage is higher than the predetermined value. The drive control device increases a value of the constant current at the mode change to be larger than a value of a constant current when the opening degree of the refrigerant passage is changed in the first mode.