A butt welding apparatus, a butt welding method, and a product manufactured by the butt welding method involves two electrode rollers disposed on both the front and back sides of a thick sheet member and a thin sheet member whose end surfaces are butted. The electrode rollers bridge across the sheet members and are composed of small diameter portions on the side of the thick sheet member and large diameter portions on the side of the thin sheet member. The small diameter portions come into contact with and press the thick sheet member before the large diameter portions come into contact with the thin sheet member. Thus, the end surface of the thick sheet member swells and deforms toward the thin sheet member and reliably comes into contact with the end surface of the thin sheet member, and power is applied between the end surfaces, even if not polished.