A low-voltage switching device including a plurality of arc-extinguishing chambers, wherein each of the arc-extinguishing chambers encloses a contacting unit including a stationary contact and a movable contact and arcs are formed when the movable contact is disconnected to the stationary contact, each of the arc-extinguishing chamber including a plurality of U-shaped arc extinguishing plates arranged for splitting, guiding and cooling the arc formed between the contacts and sidewalls provided with guiding means for guiding the arms of the arc extinguishing plates. The guiding means includes a plurality of supporting plates and the supporting plates are arranged protruding towards interior of the arc-extinguishing chamber for receiving the arms of the arc-extinguishing plates and for providing electrical isolation between arms of two adjacent arc extinguishing plates.