Abstract: IMPROVED RESISTANCE WELDING DEVICE that includes a mobile electrode in a support assisted by a spring, gas cylinder or expansion element, allowing its movement on being compressed so that the time lapse for the welding is sufficiently long to be effective, without altering the movement cycle of the press into which it is installed. The support has one or several columns, the electrode being supported sliding along one and with a rod housed on the inside of a positioning device, also axially movable, into which the small parts to be welded are received through a conduit. The positioning device, made from an insulated material, preferably ceramic, has some fixing clamps for said part until the welding is made pushed by the electrode rod through a lower window.