To make turnover, shoulder build-up, or the like less liable to occur at the time of stranding.

Sectorial strand 3 with outer and inner circumferential surfaces forming circular arc surfaces and both side surfaces forming flat surfaces are stranded on the periphery of a metal pipe 1. As for the sectorial strand 3, when viewed in a cross-section of the stranded wire, the radius of curvature of the circular-arc outer circumferential surface is smaller than the outer radius of a stranded-wire layer made up of the sectorial strand 3. This arrangement enables the contact width h of neighboring sectorial strand 3 to be increased and therefore the disposition of the strand is stabilized.