PURPOSE: To shorten the time of teaching play back by calculating probe moving time between respective passing points and calculating an optimum probe path corresponding to that probe moving time.

CONSTITUTION: An optimum path calculating means 7 calculates the optimum probe path by using the calculated probe moving time between respective passing points, and the track of the probe path is displayed on a display together with a design drawing. Thus, the probe path can be confirmed while shortening measuring time. A post-processor 8 prepares a part program for three- dimensional measuring instrument from the optimized probe path calculated by the means 7. For the part program, the procedure of measurement is written for automatically measuring the plural works in the same shape through the same procedure. On the other hand, by transferring the part program prepared by the post-processor 8 to a three-dimensional coordinate measuring instrument (CMM) 9, the teaching play back is executed at the CMM 9.