Classification of resistance welding specialized equipment that joins metal materials through electrical pressure and heat. Includes main body devices such as spot welding machines, seam welding machines, projection welding machines, and butt welding machines. This welding method is specialized for automotive parts, electronic equipment housings, and thin sheet metal assembly work, enabling high-quality joining in short time. As specialized equipment with integrated electrode tips, pressure cylinders, and control devices, it is optimized for continuous welding operations in mass production lines. This is an independent equipment classification with welding principles different from arc welding machines and gas welding machines.