A process for modifying the surface of a material such as plastics, metals, glasses and ceramics which comprises the steps of (1) coating a compound having at least one azido group on the surface of the material to be modified, (2) making a modifier substance to be fixed for the modification exist on or in the coated surface, and (3) irradiating ultraviolet rays to the coated surface to fix the modifier substance to the coated surface, wherein various compounds can be used as the modifier for converting the characteristics of the material surface to the desired characteristics without previously treating them, and various materials can be easily modified with a firm fixing of the modifier.