Method for fastening a roller head to a welding arm for a resistance seam welding machine, wherein the roller head has a stator and an electrode roller which is supported as a rotor on the stator in a rotatable way about a rotation axis, and wherein the stator protrudes over the electrode roller with fastening extensions on both sides of the electrode roller in the direction of the rotation axis, comprising the steps: a) providing a welding arm for a resistance seam welding machine comprising a reception opening for the roller head, which is formed between two, particularly parallel, limiting walls facing each other, which themselves have fastening reception openings for the fastening extensions of the stator of the roller head; b) arranging the roller head in the reception opening for the roller head in such a way that the electrode roller protrudes outside the reception opening with a part of its circumferential boundary and the fastening extensions are arranged inside the fastening reception openings; characterized by c) fastening the roller head to the welding arm by pressing each of the fastening extensions of the stator with an even contact surface formed thereon to an attributed even contact surface (10, 19) inside the boundaries of the respective fastening reception opening, wherein the contact surfaces of the fastening extensions of the stator and the attributed even contact surfaces have supply and discharge openings (15, 16) for a cooling medium and the fastening extensions of the stator are arranged and fastened in the fastening reception openings for the fastening extensions in such a way that each of the supply and discharge openings (15, 16) overlap at least partially, and wherein each of the fastening extensions of the stator is pressed with a clamping piece received in the respective fastening reception opening with its contact surfaces against the attributed contact surfaces (10, 19). a) providing a welding arm for a resistance seam welding machine comprising a reception opening for the roller head, which is formed between two, particularly parallel, limiting walls facing each other, which themselves have fastening reception openings for the fastening extensions of the stator of the roller head; b) arranging the roller head in the reception opening for the roller head in such a way that the electrode roller protrudes outside the reception opening with a part of its circumferential boundary and the fastening extensions are arranged inside the fastening reception openings; characterized by c) fastening the roller head to the welding arm by pressing each of the fastening extensions of the stator with an even contact surface formed thereon to an attributed even contact surface (10, 19) inside the boundaries of the respective fastening reception opening, wherein the contact surfaces of the fastening extensions of the stator and the attributed even contact surfaces have supply and discharge openings (15, 16) for a cooling medium and the fastening extensions of the stator are arranged and fastened in the fastening reception openings for the fastening extensions in such a way that each of the supply and discharge openings (15, 16) overlap at least partially, and wherein each of the fastening extensions of the stator is pressed with a clamping piece received in the respective fastening reception opening with its contact surfaces against the attributed contact surfaces (10, 19). wherein the contact surfaces of the fastening extensions of the stator and the attributed even contact surfaces have supply and discharge openings (15, 16) for a cooling medium and the fastening extensions of the stator are arranged and fastened in the fastening reception openings for the fastening extensions in such a way that each of the supply and discharge openings (15, 16) overlap at least partially, and wherein each of the fastening extensions of the stator is pressed with a clamping piece received in the respective fastening reception opening with its contact surfaces against the attributed contact surfaces (10, 19).