Abstract: A single wire steel cord is prepared by flattening a round wire to have two flat surfaces facing each other and two round surfaces interposed between the two flat surfaces to face each other, wherein a flattening ratio D/W of the wire, where D denotes the short diameter of the cross section of the flattened wire and W denotes the long diameter of the cross section of the flattened wire, falls within a range of 0.5 to 0.95. Forming is applied to the flattened wire in a direction of at least the short diameter of the cross section of the flattened wire, and the flattened single wire steel cord is embedded in a tire belt portion such that one flat surface of the cord faces that portion of the tire which is brought into contact with the ground.