PURPOSE: To improve positioning precision of a moving body, to hold the position of the moving body during a stop, to reduce the weight of a moving part, and to perform movement of the moving body at a high speed.

CONSTITUTION: A moving mechanism is provided with a pair of racks 12a and 12b disposed in parallel to a moving body 46, and moving bodies 16a and 16b movable in parallel in the direction of the lengths of the racks 12a and 12b, and the moving body 46. The moving mechanism is further provided with a coupling body 18 having its both ends respectively coupled to the moving bodies 16a and 16b, pinion gears 28a and 28b rotatably located to the moving bodies 16a and 16b and engaged with the racks 12a and 12b, respectively, a ball screw 20 in parallel to the racks 12a and 12b and rotatably screwed in the moving bodies 16a and 16b and capable of holding a present rotation a position position when rotation is stopped, and a drive means 24 to rotate the ball screw 20.