An ignition device for an internal combustion engine has an ignition coil disposed as a transformer, a spark plug connected to the secondary winding of the ignition coil, an actuatable switching element connected in series with the primary winding of the ignition coil, and a control unit connected to the primary winding and to the control input of the switching element. After charging the ignition coil, building up an ignition spark through non-conductive switching of the switching element, and after renewed conductive switching of the switching element for operating the ignition coil in transformer operation, the supply voltage of the control unit is detected and if a pre-determined value, representing the presence of a surface gap, is exceeded, the switching element is once more switched non-conductive.