PURPOSE: To improve workability by efficiently measuring the position of a work fixed on the table of a machine tool.

CONSTITUTION: A spindle 8 fitted with a measuring instrument S and a table 2 fixed with a work W are relatively moved via manual actions to measure the position from a machine origin of the work fixed to the table 2 of a machine tool controlled by a numerically controlled device 9, positions of a spindle 8 and/or the table 2 are automatically automatically read by the numerically controlled device 9 when the measuring instrument S is brought into contact with the work W, the positions of necessary points are read then automatically calculated and written into a memory area.