To provide a high strength and high fatigue strength steel for a saw wire, having higher tensile strength, capable of making the saw wire more thin, and excellent toughness and ductility.

The composition of a saw wire contains, by mass%, C:0.18 to 0.30%, Ni:6.0 to 9.0%, Co:8 to 20%, Mo:1.0 to 6.0%, Cr:1.0 to 6.0%, Al:0.5 to 1.3%, Ti:≤0.1%, N:≤0.010%, O:≤0.010% and the balance Fe with inevitable impurities.