Surface-treated steel sheet

A surface-treated steel sheet comprising a chemical conversion coating with a thickness of 0.1 μm or more and 1.0 μm or less, the chemical conversion coating being placed on a surface of a hot-dip Zn—Al alloy coated steel sheet including a hot-dip Zn—Al alloy coating film containing Al:

• more than 1.0 mass % and 15 mass % or less, a balance being Zn and inevitable impurities,
• wherein the chemical conversion coating contains AlH2P3O10.2H2O and a compound containing one or more elements selected from Mg and Sr such that a sum of contents of AlH2P3O10.2H2O and the compound is 3.0 mass % to 50 mass %, and
• wherein the hot-dip Zn—Al alloy coating film further contains at least one selected from groups A and B
• group A:
• Mg:
• 0.1 mass to 10 mass %;
• and
• group B:
• one or more elements selected from Si, Ca, Ti, Cr, and Ni such that a sum of contents of the elements is 0.01 mass % to 1.0 mass %.