PURPOSE: To improve working efficiency by providing a control device whereby the operation of a rack-driving device is controlled according to a set value for a pathway width-setting device and the rack is so shifted that a working pathway with a pathway width corresponding to the set value is formed.

CONSTITUTION: Each of pathway-forming switches SW1, each of pathway width- setting switch SW2 and each of rack-shifting motors M are connected to a control device A. When the pathway-forming switch SW1 is pushed, the title device is so composed that a working pathway P having a pathway width corresponding to a set value for the pathway width-setting switch SW2, is formed. That is to say, when some of the pathway-forming switches SW1 for racks of 1 to 8 are pushed, each of the racks to be shifted in order that the working pathways 9 are formed at the places corresponding to their switches SW1, and their directions, is decided in a deciding circuit B for the rack and the direction to be shifted. Furthermore, an operation command is transmitted to a motor-driving circuit C to be required through the deciding circuit B, and a rack-shifting motor M corresponding thereto is driven. In this way, each of the racks is shifted according to the decision of the deciding circuit B.