An expansion device capable of preventing an abnormal increase in the high-pressure in a freezing cycle and having, as an integrated unit thereof, a mechanism capable of quickly responding to an abnormal increase in the high-pressure and the low-pressure is provided. A means for displacement (bellows) 28 which becomes displaced in correspondence to the high-pressure is linked to a valve element 24 of a restrictor valve mechanism 32 to displace a rod 34 provided with a safety valve mechanism 33. If the high-pressure reaches a level equal to or higher than a first specific pressure (the limit to the normal operating pressure), a first portion 26 of the safety valve mechanism 33 becomes disengaged from a relief hole 27 that communicates between a high-pressure space 29 and a low-pressure passage 31 to be replaced by a second portion 25 which allows passage through the relief hole 27, thereby leaking the coolant in the high-pressure space 29 to the low-pressure passage 31 and preventing a further increase in the high-pressure. In addition, a low-pressure side rupture disk mechanism 40 that becomes ruptured if the low-pressure reaches a level equal to a second specific pressure to communicate between the low-pressure passage 31 and the atmosphere is provided at the low-pressure passage 31. A high-pressure side rupture disk mechanism 50 that becomes ruptured if the high-pressure reaches a level equal to or higher than a third specific pressure to communicate between the high-pressure passage 30 and the atmosphere is provided at the high-pressure passage 30.