An ejector for a refrigerating machine having a main body crossed by a conduit for passage of refrigerant fluid and having a compartment which includes a seating, which is in communication with the conduit, and a mouth for inlet of refrigerant fluid; a nozzle which can be coupled with the seating and has an internal hole for passage of the refrigerant fluid, and a shutter having an end which can be coupled with the hole to close the hole.