PURPOSE: To perform projection welding while positioning each material to be welded by providing a positioning pin and a recessed part in which the same pin is fitted on each electrode platen or even if a through hole for positioning where a pin passes through material to be welded is not provided.

CONSTITUTION: Conical projections 22 and 32 are formed in a body, respectively on the respective welding faces 21 and 31 of materials 20 and 30 to be welded and cylindrical small projections 22a and 32a are formed in a body, respectively on the tops of the same projections 22 and 32. Meanwhile, small holes 23 and 33 having the inside diameters almost equal to the outside diameters of the same small projections 32a and 22a are formed at the positions in opposition to the small projections 32a and 22a on the respective welding faces 21 and 31. In performing welding, the welding faces 21 and 31 are opposed to each other, the small projections 22a and 32a are fitted into the small holes 33 and 23, electrode platens 41 and 42 are energized and the respective welding faces 21 and 31 are subjected to projection welding.