A clamp/alignment mechanism has: a turntable on which a recording medium is mounted, the turntable being rotated by a rotation driving device; a holding device for holding the recording medium mounted on the turntable; an aligning device for aligning the recording medium mounted on the turntable; and a driving device for driving both the holding device and the alignment device. The driving device is configured to drive the aligning device in an aligning direction along which the recording medium is subjected to alignment thereof, in cases where the holding device is driven in a holding direction in which the recording medium is to be held.