PROBLEM TO BE SOLVED: To provide a novel rust prevention treatment method capable of imparting excellent rust prevention performance to various kinds of metallic materials such as zinc or aluminum.SOLUTION: In a rust prevention treatment method of a metallic material, after applying chemical treatment by treatment liquid containing a trivalent chromium compound to the metallic material, as the need arises, chemical treatment by treatment liquid containing a phosphate is allied thereto, and then a siliceous coating is formed by using treatment liquid containing an alkoxysilane oligomer.