The topic of this thesis is robotic welding of the bottom of a transformer tank. In the first, theoretical part of the work, welding technology is described and the most common welding procedures are briefly described. Since the MAG welding procedure was applied in the experimental part, it is described in more detail with the parameters related to the geometry of the weld. Since solid wires and powder-filled wires (FCAW) can be used in the MAG process, they are briefly compared. The advantages and disadvantages of the procedure, welding equipment , examples of application of the procedure are shown and finally, the mistakes that most often occur with the mentioned procedure are shown and described. Robotic welding is explained and the types of robot programming were described. At the beginning of the experimental part of the work, the product that was robotically welded was explained. The programming of the robot is explained in detail, the test station where the welding was performed is described, and the robot which was used is described. Furthermore, the adjustment of the robot that needs to be done before starting welding is explained. The modern CMT MIG/MAG procedure used is described, and it is a representation of the sequence of robotic welding. The obtained geometry of the weld is presented and at the end a penetrant test was performed.