To provide a ball screw nut and a manufacturing method thereof having a ball rolling groove reducing vibration and noise, and excellent in durability.

Shot peening treatment is performed by disposing a nozzle for jetting media toward a circulation line disposed in an inside diameter surface 1a of the nut, and injecting the media into the ball rolling groove 2 formed on the inner peripheral surface of the ball screw nut 1. In this example, the media is injected from one direction of the right side surface of the figure of the ball screw nut 1. The media is also injected from a let side direction of the drawing of the ball screw nut 1. The media is injected with the angle of approximately 45 degrees with respect to the inside diameter surface 1a of the ball screw nut 1.