A closure device for an electrical plug-in coupling arranged on a motor vehicle or a charging station. A locking arrangement is provided for locking the plug coupled to the plug-in coupling. The locking arrangement can be operated via a gear mechanism between the drive motor and the closure flap. The locking arrangement has a locking element which, when the closure flap is transferred from an intermediate open position, in which the plug can be coupled to the plug-in coupling, into the final open position, can be brought into a locked position which prevents the removal of the plug from the plug-in coupling.