The closeable opening device according to the invention comprises a base (2) in which a cutting element (3) is supported. Driving dogs (42) in the closing screw cap (4) engage with driving dogs (32) in the cutting element (3), so that the cutting element (3) is displaced in the base (2) to the end position upon initial opening. At least one first rotational stop (5, 50) ensures that the cutting element remains in position and neither moves upward in an undesired manner when the screw cap is opened, nor can be displaced downward by any relative displacement of the two parts, thus causing same to fall into the container. The first rotational stop (5) is made of a rib (50) on the inner face of the spout (20), which interacts with a recess in the form of a flat spot (35) on the cutting element (3). A second rotational stop (5) made of a stop cam (52) can additionally be present at the spout end (51) of the inner thread (24) in the spout (20), against which the inlet end (36) of the outer thread (31) on the cutting element (3) is stopped. When using both rotational stops (5), an end position of the cutting element (3) is secured in a form-fit as well as force-fit manner in the base (2).