The bronchus blocker according to the invention comprises an insertion rod and a blocking means. The blocking means is provided near one end of the insertion rod in order to be inserted by means thereof into a bronchus. The bronchus blocker furthermore comprises a support, for supporting the bronchus blocker on a bronchial branching, such as the carina. By supporting the bronchus blocker on a bronchial branching using its support, the inflated balloon only has to seal the bronchus and does not also have to keep the bronchus blocker in its position at the same time. As a result, the risk of the bronchus blocker slipping out of its position is much smaller than with the prior art.