PURPOSE: To prevent the deflection of carriages and blurring in high-speed scanning by providing 1st and 2nd scanning transmission means which are respectively spanned on one side and the other side of 1st scanning means and 2nd scanning means and mounting means which mount the 1st scanning means scannably to 1st guide means.

CONSTITUTION: The 1st carriage 32 is mounted on one side to a screw shaft 42 and a 2nd wire 51 is extended on the 1st guide rail 43 side on the other side. Since the deflection between the two carriages 32 and 36 is regulated, the carriages do not oscillate or deflect on the 1st guide rail 43 side even if the scanning is executed at a high speed of ≥300[mm/sec] and 60[times/min] number of scanning times. The 2nd carriage 36 is set at 1/2 this scanning speed; in addition, this carriage carries two sheets of mirrors and is heavy and, therefore, the carriage is scanned stably without oscillating. The generation of the deflection and blurring of the images by the deflection and oscillation of the carriages is obviated in this way and the good images are obtd.