To prevent generation of a welding defect due to too much/too little welding electric current among each metal group of a low electric resistance and of a high electric resistance respectively even when a butt resistance welding is conducted among clad metals themselves composed of a high electric resistance metal and a low electric resistance metal.

High resistance layers 1a and 2a composed of a high resistance metal with a high electric resistance, and low resistance layers 1b and 2b formed on a surface of the high resistance layers 1a and 2a, comprising of a low resistance metal whose electric resistance is lower than that of the high resistance metal, comprise the first and the second clad metals 1 and 2, and the butt resistance welding is conducted among/between each end face. At this time, a groove 3 is installed only to and between the low resistance layers 1b and 2b of the butted first and second clad metals, and at the starting stage of resistance welding to flow a welding electric current, priority is given to the high resistance layers 1a and 2a of the first and second clad metals and 2.