A surface-treated steel sheet includes a steel sheet; a plating layer containing at least one metal selected from zinc and aluminum; a first layer film containing (.alpha.) 1 to 2000 mg/m.sup.2 of silica in terms of SiO.sub.2, (.beta.) a total of 1 to 1000 mg/m.sup.2 of phosphoric acid groups in terms of P, (.gamma.) a total of 0.5 to 800 mg/m.sup.2 of at least one metal selected from Mg, Mn, and Al, and (.delta.) 0.1 to 50 mg/m.sup.2 of a tetravalent vanadium compound; and a second layer film formed to a thickness of 0.1 to 5 .mu.m on the first layer film and containing a resin (A) having at least one type of functional group selected from OH and COOH groups, and at least one rust-proofing additive (B) selected from (a) a phosphate, (b) Ca ion-exchanged silica, (c) a molybdate, (d) silicon oxide, and (e) at least one organic compound selected from triazoles, thiols, thiadiazoles, thiazoles, and thiurams.