PURPOSE: To make it possible to position an end surface with a high accuracy by expanding and distributing a vector of a two-dimensional direction vertical to the end surface for positioning a workpiece into minimum command units of X and Y axes and storing them as a one-dimensional vector.

CONSTITUTION: In the case an end surface of a workpiece is placed obliquely relative to X and Y axis directions of a movable table, vector P of a vertical direction relative to the end surface to be positioned in advance is expanded to images by a minimum command unit (d) in X and Y axis directions by means of a vector expanding means 61 and they are stored in a memory buffer 64 of an MCU program 4. Then, an interpolation data takeout means 62 takes out the images one by one as interpolation data. A positioning signal output means 63, using the data sent in one by one as interpolation data, drives motors for driving X and Y axes to move the workpiece obliquely along the directional vector P and to perform positioning. Thus, positioning of the end surface of the workpiece can be performed with a high accuracy.