A clamping device that fixes a disc onto a spindle motor that rotates the disc includes a clamp ring that is layered on the disc, and a screw that fixes the clamp ring onto the spindle motor, and has a seating surface that inclines relative to a plane perpendicular to an axis of the screw, the seating surface of the screw having an inclined angle greater than a plane that contacts the seating surface of the screw of the clamp ring before the clamp ring is fixed by the screw.