PURPOSE: To simplify the program, and reduce program miss by only designating a tool with a T code to select an assisting tool rest freely.

CONSTITUTION: In ordinary, T code is used for designating a tool for the program of each tool rest, and in this device, T 0100 is used for a first tool rest, and T 2100- is used for a second tool rest, and both the two T codes are used for a third tool rest at need. At the time of assisting a first main spindle, T 5100 is used, namely, T code at a level of the number 5000 is used, and at the time of assisting a second main spindle, T 7100- is used, namely, T code at a level of the number 7000 is used. Consequently, a programmer can program the processing assisting program of the first and the second main spindles without consideration of an indexing position of a tool so far as he/she does not mistake the designation of T code.