The invention provides a surface treating agent which can form a coating film with corrosion resistance, hydrophilicity, hydrophilicity continity, dirt resistance (dust adhesion resistance) to hydrophilic dust and hydrophobic dust. The problems can be settled through utilizing the surface treating agent which comprises the components of an aqueous solvent, at least two water-soluble resin adhesives and porous resin particles (C). One water-soluable resin adhesive (A) in the at least two water-soluable resin adhesives is a polymer or copolymer of a monomer which is composed of more than one functional group selected from carboxylic acid group, sulfonic acid group, hydroxyl and acylamino, or a salt of the polymer or the copolymer, a mixture which comprises more than one selected from the polymer, the copolymer and the salt. A water-soluble resin adhesive (B) which is different from the water-soluble resin adhesive (A) in the at least two water-soluble resin adhesives is amino resin.