PURPOSE: To make a guide roller with a small diameter, reduce the cost, and prevent slip of an endless belt by installing a minor diameter pulley on the stationary side of a moving pulley in a device which moves a slider with a difference in the moving amount between the major and minor pulleys of the moving pulley.

CONSTITUTION: When a drive motor 3 is operated, a drive pulley 4 rotates, and also an idler pulley 5 coupled therewith through an endless belt 6 and the minor pulley 7a and major pulley 7b of a moving pulley 7 are put in rotating. A slider 8 moves in the horizontal direction due to the difference in the moving amount on the circumference between the minor and major pullers 7a, 7b. Therein the minor pulley 7a is located on the side nearer the slider 8 while the major pulley 7b located on the outside of the minor pulley 7a about the slider 8. That is, the minor pulley 7a is positioned on the stationary side of the moving pulley 7. This permits guide rollers 9c, 9d to be made in small diameters, suppressing the cost, and decreasing slip of the endless belt 6.