PURPOSE: To simplify teaching work and to reduce time by teaching only one point of a reference point, reading welding loci, welding conditions and torch angles from a storage means in accordance with said one point and giving working instructions.

CONSTITUTION: The tip of a welding torch is brought to a reference point P0 to teach a welding pattern. The tip is brought to the point P1 to teach a welding pattern. Similar teaching operation are repeated with P2, P3 as well. After the torch is rotated 180°, the above-mentioned teaching operations are repeated with points P4WP7 as well. However, the welding patterns used at the points P0WP3 are used for the welding pattern after the rotation by 180°. Since errors in setting of the work, position deviation, etc. arise after the rotation by 180°, it is desirable to perform teaching even after the rotation by 180°.