To effectively use an attitude data of one articulated robot of which an attitude is found to the other articulated robot and to shorten time required for off-line teaching for the two units of the articulated robots arranged at roughly symmetrical positions to a reference surface.

The attitude data of one articulated robot 50L of which the attitude is found is displayed on a pass table 110, and a mirror reflection attitude data is found by mirror-reflective transformation on the reference surface S. Thereafter, a coordinate data of a gun unit 52R of the other articulated robot 50R arranged at the roughly symmetrical position to the reference surface S is extracted from the mirror reflection attitude data, and an angle of each axis of the second articulated robot 50R is computed from the coordinate data and each parameter.