Provided is a chromium-free chemical conversion treatment technique that makes it possible to form a conversion layer excellent in corrosion resistance and appearance without using fluorine and hydrogen peroxide. The chemical conversion treatment liquid is for forming a conversion layer on zinc or zinc alloy and free of chromium, hydrogen peroxide and fluorine, includes 0.5 g/L to 38 g/L of magnesium, 0.5 g/L to 3.5 g/L of silicon, and 0.36 g/L or more of nitrate ion, contains the silicon as a water-soluble silicate, optionally further includes cobalt at a concentration of 5 g/L or less, and has an aluminum content of 0.08 g/L or less.