PURPOSE: To make a distance between top and bottom guides measurable simply and very accurately, by making full use of a numerical control (NC) system and a servo system both being intrinsically indispensable for a wire-cut electric-discharge machine.

CONSTITUTION: In case of the measuring method of a distance between top and bottom guides in a wire-cut electric-discharge machine, a first jig or a conventional jig, having two probes and making a connecting line of tips of these probes at a right angle with the bottom surface, is placed on a workpiece mounting stand 41 at a horizontal level, and an electrode wire 1 is made to be perpendicular between top and bottom guides 31 and 32. Next, a second jig 22, making the connecting line of tips of these probes at an angle (90°-θ) with the bottom surface, is placed on the horizontal level stand 41, using an NC system which moves the top guide 31 horizontally by means of a servo system, and finds its distance l. On the basis of a tilt angle θ and the distance l, the distance between top and bottom guides is found from the following equation d=l.tan-1θ.