To prevent the positional precision of the ball return passage and the tongue of the end deflector relative to the nut main body from being impaired by an axial force applied by a screw used for securing the end deflector to the nut main body, the end deflector includes a flange (32) provided at an axial end of a main part (30) of the end deflector and provided with an axial through hole (50) for receiving a screw which is threaded into the nut main body, and a rib (52) projecting from a radially inner edge of the flange to an inner side of the deflector receiving recess (26).