A drilling device includes a drill chuck which is provided with at least two adjustable clamping jaws slightly rotatably guided in the drill chuck and including a guide surface for a tool shank of a tool. The guide surface is provided with at least one projection extending in direction of the chuck axis and engaging into a recess of the tool shank for rotating and axially limiting the play of the tool. The projection of each jaw is arranged circumferentially rearwardly offset to the mid-plane of each clamping jaw so that the guide surface is defined by a leading part which is wider than a trailing part in circumferential direction of the tool shank.