A ground-drilling device includes a basic body and a drill head movably mounted in relation thereto in the longitudinally axial direction, wherein a free space, which is variable in its size owing to the movable mounting, is formed between the drill head and the basic body, and a sealing element for sealing the free space with respect to the environment, wherein the sealing element is designed as a valve element which opens when an overpressure is present inside the clearance, in order to produce a pressure compensation, and which is closed when a negative pressure is present inside the clearance, in order to prevent a pressure compensation.