To propose an upper electrode supporting device, which freely and easily supports a welding gun on a plate-like electrode in a spot welding machine in which a work clamped vertically on the plate-like electrode, which is a lower electrode, is welded by the welding gun of the upper electrode.

The device is a welding gun supporting device of a spot welding machine which welds a work W to be welded while clamping the work between a plate-like electrode 11 as a lower electrode 10 and a welding gun 21 as an upper electrode 20. The device is composed as follows: the welding gun 21 is supported by the front end of a supporting arm 30 extending over the plate-like electrode 11; the supporting arm 30 comprises a plurality of divided arms 31, 32, 33, which are connected; a pair of upper and lower fixed plates 45, 46 laterally projecting from the opposing end part of the divided arm 32, one arm of a set of adjacent divided arms 31, 32, which is at least one set of the divided arms 31, 32, 33, are provided; and a fixed shaft 42 is provided between the fixed plates 45, 46 so that one divided arm 31 is rotated around the other divided arm 32 on the fixed shaft 42.