A device for applying a decorative strips (3, 4, 5, 6) with positional accuracy to a seat cover (2) with high-frequency welding, includes two tool halves (10, 30), of which one tool half has at least one electrode (14, 15, 16, 17). A first tool half (10) has at least two electrodes (14, 15, 16, 17) oriented parallel to each other, the width of the electrodes being adapted to the width of the decorative strips (3, 4, 5, 6) to be applied. Insulators (18, 19, 20, 21, 22) oriented in parallel are arranged between the electrodes (14, 15, 16, 17) and in parallel on the outside of the electrodes. The insulators (18, 19, 20, 21, 22) protrude beyond the electrodes (14, 15, 16, 17) in the direction of the second tool half (30). The insulators (18, 19, 20, 21, 22) are height-adjustable relative to the electrodes (14, 15, 16, 17).