A sparking plug with a central electrode (2) insulated against the plug thread and earth electrodes (8, 9) electrically connected to the plug thread, in which a prism-shaped cap (7) is arranged at the end of the central electrode in the combustion chamber and the earth electrodes are parallel to the sides of the prism of the cap (7). The earth electrodes (8, 9) consist of at least one holder (8A, 8B; 9A, 9B) of a base or semi-precious metal on which a thin electrode layer (8C, 9C, 10C) of platinum or a platinum alloy is arranged facing the cap (7) of the central electrode (2).