An arc-extinguishing unit structure for a direct current air circuit breaker according to one embodiment of the present disclosure comprises: a plurality of grids; side plates coupled to both sides of the plurality of grids so that the plurality of the grids are mounted so as to be spaced apart from each other; an exhaust cover positioned above the side plates and the plurality of grids; an arc guide coupled to the side plates so as to be located under the plurality of grids; a magnet coupled to the arc guide, wherein the magnet is magnetized with different poles on the basis of the plurality of grids and the vertical orientation of the arc guide.