There is provided a ball screw apparatus ensuring easy and proper centering between a nut and a stationary member. Therefore, the ball screw apparatus (1) has a threaded shaft (10), a nut (20) that passes through the threaded shaft (10) and is screwed via a rolling body B into the threaded shaft (10) so as to be disposed movable in the axial direction of the threaded shaft (10), and a stationary member (40). The stationary member (40) is secured to an end surface (20a) of the nut (20), and a dustproof member (60) that prevents entry of foreign matter into the nut (20) is secured to the stationary member (40). The end surface (20a) of the nut (20) is provided with a spigot joint portion (20b) fitted to an outer circumferential surface (42a) of a flange part (42) of the stationary member (40).