PURPOSE: To enable plural and simultaneous welding and to rationalize welding, by making the upper electrode for projection welding consisting of upper and lower electrodes displaceable according to the deformation of a product.

CONSTITUTION: A titled electrode is formed of a lower electrode 4 and an upper electrode 10, a mechanism for moving the electrode 10 freely unrestrictedly according to the deformation condition of a product, for example, upper electrode holers 12, 13, and a bead support guide 14. The electrode 10 is held freely rotatably in the spherical seats of the holders 12, 13 by such electrode construction. Plural and simultaneous projection welding is made possible and welding work is rationalized in the stage of welding the parts deformed by plastic working, etc.