Nine vibration isolating mounts are disposed on a pedestal, and a granite plate is placed thereon. A pair of guide bases are disposed on the granite plate, and disposed thereon are a pair of posts made of CFRP for movements in a Y-direction relative to the granite plate. A beam made of CFRP is extended between the pair of posts. Further, a movement base is disposed for movement in an X-direction relative to the beam, and a laser optical unit is mounted on the movement base.