A robot base 15 is installed on a ceiling 100, and a first wrist element 11 is attached to a front arm base 10 to be rotatable about a first axis A. A second wrist element 12 is attached to the first wrist element 11 to be rotatable about a second axis B, and a welding torch 2 is supported via a transmission mechanism 13 to be rotatable about an offset axis C. The welding torch 2 is attached so that a tip end thereof is directed downward in the illustrated posture of the robot. A linear guide 6a and a slider 7 are provided via a support base 5, and an intermediate portion of a torch cable 3 (or a welding wire delivery device 4) is fixed thereto to draw a tensioning device 80. Such a structure is applicable to a wall-hanging type robot. Thereby, a structure for treating a torch cable is realized in an arc welding robot of a ceiling-suspension type/a wall-hanging type, capable of maintaining the behavior of the torch cable in a stable state as well as minimizing the interference of the torch cable with other objects.