an indirect system spot welding machine in which the jig grasps a work via the material handling robot , said jig being comprised of a work clamper portion to clamp and fix the work and an earth clamper portion to connect the work to the terminal of an earth cable at a welding transformer side , the spot welding machine being provided with a lifting mechanism for supporting an electrode and another lifting mechanism for supporting a back bar , independently , to shorten the length of the earth cable to be used and eliminate the necessity of the particular jigs for the work positioning and to prevent pressed trace by the spot electrode from the products .