A method for forming a multilayer coating film, the method comprising forming a chemical conversion coating film and an electrodeposition coating film on a metal substrate by the following steps: Step 1: immersing a metal substrate in a chemical conversion treatment solution to form a chemical conversion coating film without the application of electric current; and Step 2: performing electrodeposition coating on the metal substrate by using a cationic electrodeposition coating composition to form an electrodeposition coating film, wherein the chemical conversion treatment solution contains less than 100 ppm of sodium ions on a mass basis, the chemical conversion treatment solution contains less than 90 ppm of calcium ions on a mass basis, the chemical conversion treatment solution contains less than 100 ppm of potassium ions on a mass basis, the chemical conversion treatment solution contains less than 90 ppm of magnesium ions on a mass basis, the chemical conversion treatment solution is used continuously, and either (i) industrial-water washing and/or clean-water washing or (ii) pure-water washing is performed, or neither (i) nor (ii) is performed after the chemical conversion treatment and before the metal substrate having a chemical conversion coating film formed thereon is immersed in a cationic electrodeposition bath, wherein the cationic electrodeposition coating composition contains an amino group-containing epoxy resin (A) and a blocked polyisocyanate (B), the amino group-containing epoxy resin (A) being contained in an amount of 40 to 90 mass%, and the blocked polyisocyanate (B) being contained in an amount of 10 to 60 mass%, based on the total resin solids content. Step 1: immersing a metal substrate in a chemical conversion treatment solution to form a chemical conversion coating film without the application of electric current; and Step 2: performing electrodeposition coating on the metal substrate by using a cationic electrodeposition coating composition to form an electrodeposition coating film, wherein the chemical conversion treatment solution contains less than 100 ppm of sodium ions on a mass basis, the chemical conversion treatment solution contains less than 90 ppm of calcium ions on a mass basis, the chemical conversion treatment solution contains less than 100 ppm of potassium ions on a mass basis, the chemical conversion treatment solution contains less than 90 ppm of magnesium ions on a mass basis, the chemical conversion treatment solution is used continuously, and either (i) industrial-water washing and/or clean-water washing or (ii) pure-water washing is performed, or neither (i) nor (ii) is performed after the chemical conversion treatment and before the metal substrate having a chemical conversion coating film formed thereon is immersed in a cationic electrodeposition bath, wherein the cationic electrodeposition coating composition contains an amino group-containing epoxy resin (A) and a blocked polyisocyanate (B), the amino group-containing epoxy resin (A) being contained in an amount of 40 to 90 mass%, and the blocked polyisocyanate (B) being contained in an amount of 10 to 60 mass%, based on the total resin solids content. <EOS>