PURPOSE: To make the moving accuracy of a Y rail or pen carriage by fastening between a rack rail and a pinion gear more precise by a method wherein lateral movement of the Y rail in the X axis direction of an X-Y plotter main body and sliding of the pen carriage in the Y axis direction of the Y rail are performed by a fastening mechanism between the rack rail and pinion gear.

CONSTITUTION: Moving of a Y rail 12 to an X-Y plotter main body 11, or moving of a pen carriage 13 to the Y rail 12 is performed by the rotation, driving for which fastening between a rack rail 22 or 23 and a pinion gear 23 or 33, and rotational movement of a pinion roll 29 or 39 to a flat rail 28 or 38 are cooperated. For the moving of the Y rail 12, the pinion gear 23 which is practically integrated with the Y rail 12 is fastened to the rack rail 22 which is integrally formed with the X-Y plotter main body 11 and the flat rail 28 which is provided in parallel with this rack rail 22, and at the same time, the pinion roll 29 gives rotational movement, and at least the pinion gear 23 is rotation-driven by a motor 26.