To provide a spot welding gun having versatility and simplified structure.

The spot welding gun 1 has intermediate electrodes 10 and 30, and intermediate electrode arrangement holding means 20 and 40. When a portion in which the generation of indentation is not permitted is welded, the intermediate electrodes 10 and 30 are arranged at a holding position, and the intermediate electrodes are interposed between a gun arm and a work to perform the spot welding, and thus the indentation in the work is prevented. When a portion in which the presence of indentation is permitted is welded, the intermediate electrodes 10 and 30 are arranged at a retreat position, the intermediate electrodes are retreated from a part between the gun arm and the work to perform the spot welding, and the work is welded with a high bonding strength.