A disk drive includes a turntable and a clamper. The turntable and/or the clamper have four or more projections, each of which has predetermined height. The projections are arranged at positions for supporting/holding a mounted disk by using the four or more projections, wherein the projections are located at substantially equal intervals around a circumference of the turntable/clamper and the tips of the projections are substantially in the same plane.