<p>A surface-treating agent mainly includes three constituents: a water-soluble polymer; a surface sizing agent which is a copolymer of a styrene type monomer and an anionic monomer and which mainly includes a water-soluble copolymer containing 20 to 80 weight % of the styrene type monomer; and a surface sizing agent which is a copolymer of an olefin type monomer and an anionic monomer and which mainly includes a water-soluble copolymer containing 20 to 80 weight % of the olefin type monomer. The surface-treating agent is coated and dried on a base paper for offset printing.</p>
