A ball screw device for reducing damage to a circulating part even during a high speed operation is provided. To this end, the circulating part includes a pair of legs having a tang to scoop up a ball in a direction substantially match with a tangential direction of a spiral path, and a body to connect the pair of legs, wherein a center path diameter Rb of the ball, an internal diameter Rn of the nut, and an internal diameter Rt opposite to the tang satisfy a relationship of Rb ≦Rt≦Rn.