PURPOSE: To perform forming work easily in a short time by providing a die, which has greater electric resistance and strength than an electrode base material, at the tip of the electrode of a resistance welder.

CONSTITUTION: Dies 3 and 4 made of materials which have greater electric resistance and strength than electrode base materials and also have superior heat resistance, wear resistance, etc., are attached to tip parts of upper and lower electrodes 1 and 2, and a material 5 to be worked is fed with electricity and pressed to perform necessary forming work. During feeding and heating operation, if those tip dies come into direct contact with each other, they are molten, so when they need to come into contact, insulating materials are provided over die contacting surfaces to form insulating layers 6.