Device for cutting out the vent of the carcass of poultry during a slaughtering process, comprising a hollow cylindrical knife having a cutting edge at its distal end, a vent centring pen arranged within there, and extending parallel to the centre axis of the knife, means for rotatingly driving the knife and means for rotatingly driving the centring pen in opposite direction, the cutting edge of the knife having inclined cutting edge portions, which include an obtuse angle opening in the rotation direction of the knife, with the proximal direction component of the centre axis of the knife, as seen in a projection plane which contains the centre axis of the knife, and the centring pen being provided with elevations protruding from its surface, having engaging surfaces which are arranged in helical line, which helical line encloses an obtuse angle opening in a rotation direction opposite to that of the knife with the proximal direction component of the centre axis of the knife, as seen in the projection plane.