A steel cord for a tire reinforcement having a non-circular cross-section includes: a lower strand; and an upper strand that surrounds an outer circumferential surface of the lower strand so as to have an m+n structure, wherein the lower strand includes a plurality of core wires, each of the plurality of core wires have a flat surface on a portion in which the plurality of the core wires come into contact with each other, and the plurality of core wires come into surface contact with each other through the flat surface.