An ejector device adapted to generate a negative pressure with compressed air, which via a compressed-air duct is fed to an ejector, the device including a valve member arranged in the compressed-air duct and controllable in order to, in the open position, allow flow of compressed air to the ejector, an air suction duct arranged between the ejector and a gripping member driven by negative pressure, and a vent valve fluidly arranged with the air suction duct and that, in an open position, places the gripping member in communication with the atmosphere. The valve member embraces: a primary valve arranged in the direction of flow of compressed air; a secondary valve arranged downstream of the primary valve; a flow section of compressed-air duct between the primary and secondary valve, the vent valve communicating with the flow section so that, in the open position of the primary valve, is continuously being subjected to a closing air pressure, independently of the open or closed position of the secondary valve.