A valve body 10 of an expansion valve 1 comprises a valve chamber 14 to which refrigerant from a compressor is supplied. The amount of refrigerant is controlled between a valve member 40 and a valve seat 16, and travels through a first passage 20 to an evaporator. The refrigerant returning from the evaporator travels through a second passage 50 and into the compressor. The valve chamber 14 is equipped with a bypass passage which is communicated through a narrow hole 24 to an opening 26 with a bottom, and through a conduit 28 to the first passage 20. The electromagnetic valve 100 comprises a plunger 130, and opens/closes the bypass passage by a pilot valve 150. A pressure switch 220 is equipped to an opening 54 communicated to the second passage 50, and when the pressure of the refrigerant returning from the evaporator is reduced, the valve 100 is operated and the bypass passage is opened.