This paper presents a novel graft copolymerization method which allows for surface modification with micron-order regional precision. The essential feature of the method is based on surface photoprocessing leading to immobilization of radical initiators. This method consists of the following steps : (1) derivatization of amino groups onto a polymer surface via photochemical fixation of poly(allylamine) partially derivatized with photoreactive phenylazido groups, (2) chemical fixation of carboxylated radical copolymerization initiators via condensation reaction with poly(allylamine), and (3) surface radical graft copolymerization under reduced pressure. Two examples were demonstrated to verify the effectiveness of this method. One was surface graft copolymerization of styrene on poly(vinyl alcohol) (PVA) film, and the other was surface graft copolymerization of acrylamide on poly(ethylene terephthalate) (PET) film. Electron spectroscopy for chemical analysis (ESCA) and water contact angle measurement before and after sequential surface reactions provided evidence that graft copolymerization proceeded successfully. The microprocessing of a substrate surface using a photomask with micron-level spaces was demonstrated. Microscopic observations of modified surfaces using an atomic force microscope (AFM) showed that surfaces were grafted on only UV-irradiated regions, resulting in the formation of a micropatterned graft polymer, which was clearly visualized by staining of hydrolyzed acrylamide units with a dye. The scope of potential applications is discussed.