PURPOSE: To provide a surface-treating agent for applying antistaticity to a sheet of synthetic paper, plastic film, etc., to be printed by offset printing and to provide a process for producing a sheet for offset-printing.

CONSTITUTION: The surface-treating agent is composed of an aqueous composition obtained by combining (A) an ionic conductive resin composed of a partially cross-liked water soluble copolymer produced by the copolymerization of (i) a monofunctional vinyl monomer having cationic quaternary ammonium base on side chain and polymerizable double bond at molecular terminal, (ii) a bifunctional vinyl monomer having hydroxyl group and (iii) other polymerizable monomer with (B) a thermally cross-linking monomer at a ratio within a specific range. The surface-treating agent is applied to a surface of a printing sheet for offset printing and cured with heat to obtain a sheet for offset printing.