PURPOSE: To weld fully automatically a housing with one unit of robot by controlling the rotative movement of the welding tool of the welding robot in four axis directions.

CONSTITUTION: A work 1 is positioned upside down and is set to a work holding member 35 on a jig 3. A welding gun 4 is set to each welding position of the work 1 by operating manually each motor of a robot 2 and the point on the route traced by the gun 4 is read by each axis by a digital detector and is stored into the storage device of the robot 2. Such teaching operation is performed with all the welding points of the work 1 and is performed while a rotating base plate 34 is rotated by 90° each at every end of the storage of the welding point on the surface of the work 1. When welding is started after such teaching operation is performed, the robot 2 and the jig 3 perform the operation in exact conformity with the stored operation. The plate 34 is automatically rotated 90° when welding of each welding position on the 1st surface of the work 1 is finished and the operation for spot welding the 2nd surface is successively repeated until the work 1 is completed.