A ball-screw spline includes: a screw shaft; a ball-screw nut engaged with the screw shaft via balls; and a spline nut assembled to an outside of the ball-screw nut via balls to reciprocate in an axial direction of the ball-screw nut. The ball-screw nut includes a screw portion and an extended portion formed integrally, with the same outer diameter. The screw portion has an inner peripheral surface including a load-rolling groove forming a load path for the balls together with a ball rolling groove on the screw shaft side; and a ball return path coupling adjacent valley portions of the load-rolling groove to form a circulation path corresponding to one loop around the screw shaft. The ball-screw nut has an outer peripheral surface including a ball rolling groove for the spline nut, the ball rolling groove being formed over a range corresponding to the screw portion and the extended portion.