The invention is directed to a device for straightening a stream of a cooling medium for cooling a roll or a metal strip. This device comprise a hollow body, extending over at least part of the width of the roll or the metal strip, and a tube, arranged in the hollow body and extending in the direction of the width of the roll or the metal strip, wherein the hollow body is divided in the direction of the width of the roll or the metal strip into a number of chambers, and the tube comprises openings for introducing cooling medium into the chambers of the hollow body, and the chambers respectively comprise an opening for the flowing out of cooling medium from the hollow body. Furthermore, according to the invention the chambers, respectively, comprise a channel, formed between the inner wall of the hollow body and the tube, for conducting cooling medium from the openings of the tube to the opening for the outflow of cooling medium from the hollow body, wherein the flow cross-section of the channel narrows art least at its downstream end.