A method for manufacturing a cord yarn, which has at least one filament strand, includes applying a first twist so that a K1 value has a value of 0.1837763/D1n or below, applying a second twist so that a K2 value has a value between 0.0166819/D2n and 0.3183099/D2n, and applying a third twist so that a K3 value has a value between 0.0278485/D3 and 0.2968288/D3, wherein the twists are applied so that the cord yarn has roundness of 50% or above, and when the filament is a multi filament, so that porosity between strands of the cord yarn is less than 40%.