An ejector having formed therein a rotation space (221) that rotates a high-pressure coolant that has flowed in from a coolant inlet port (211) inside a body (200) and guides same to a depressurization space (222) that causes the rotating high-pressure coolant to depressurize and expand. A passage-forming member (240) that forms a nozzle passage (224) and a diffuser passage (232a) has a shape having an increasing cross-sectional area the further the passage extends away from the depressurization space (222). A temperature-sensing section (252) in a drive device (250) that displaces the passage-forming member (240) is housed inside the body (200) and the temperature-sensing section (252) and a diaphragm (251) are formed in an annular shape so as to encircle at least an axis (X) of the passage-forming member (240). As a result, size increase is suppressed and operation that matches the load of a refrigeration cycle can be achieved.
