Abstract: A method for continuously electro-tinplating a metallic material comprising the steps of: using an acidic electro-tinplating solution containing phenolsulfonic acid or a salt thereof and tin ion, using an insoluble anode, and causing a DC electric current to flow between the insoluble anode and a metallic material, while replenishing the acidic electro-tinplating solution with tin ion, thereby forming a tinplating layer on the surface of the metallic material. The above-mentioned anode comprises an electric-conductive substrate, and a film comprising at least iridium oxide, formed on the surface of the electric-conductive substrate.