PURPOSE: To aim at improvements in positioning accuracy of a device and simplification in its structure as well as reduction in the cost of production, by making a conventional double-superposition construction alterable to a single-super position one and furthermore constituting a work table so as to make both directions of X- and Y-axes supportable on the same supporting surface.

CONSTITUTION: In case of a positioning device for X- and Y-axes at a plane surface, a ball screw 4 and an X-axis driving motor 3 are installed in a base 1. This screw 4 is set up in a groove part installed in the base 1, and a guide surface of a guide 10 for both X- and Y-axis is formed on top of this groove and also at a position where it does not interfere with a nut part 12 used for this ball screw. Next, the guide 10 is of solid construction in type and an X-Y axis table 11 is supported by a base supporting surface 1 comprising a single-stage construction whereby errors due to pitching, yawing, rolling, etc., produced by movements of the table 11 is made smaller, permitting of highly accurate positioning, thus simplification in the construction is well promotable.