To provide a treatment method for steel which improves a fatigue strength of the steel.

The treatment method for the steel comprises: a process (S1) of applying a quenching treatment to the steel having 0.15-0.70% carbon content; a heat treatment process (S2) of applying a tempering treatment to the steel by heating it at 250-300°C for ≥2 hr thereby transforming an austenite in the structure into a martensite; a first shot peening process (S3) of applying shot peening to the steel by using shot particles with a large diameter; and after the first shot peening process (S3), a second shot peening process (S4) of applying shot peening to the steel by using shot particles with a small diameter.