PURPOSE: To ensure inputting of a correction value, by a method wherein, on the preset chamber side, the correction value of a preset tool is stored in a computer, and after the preset tool is moved to the machining unit side, a correction value is called to confirm it by means of a display unit.

CONSTITUTION: Fig number of a workpiece is inputted to a computer 5 by means of a key board 7, and a list of holding tools and blade tools are outputted to a CRT 8 to prepare the holding tools and the blade tools. A bar code sticked to a preset tool is scanned by means of a bar code reader 11 to input the bar code. Thus, the preset figure of a tool is outputted to the CRT 8. The correction value of a position to be measured is computed, and a result is stored in a hard disc 10. The preset tool and a display device 18 are placed on a truck and are varried from the preset chamber 1 side to the machining unit 2 side. In the machine tool 12, the connection terminal of the display device 18 is connected to a cable 15, the bar code of a tool is scanned by means of the bar code reader, an output therefrom is inputted to the computer 5, and a correction value is displayed at a display unit 26.