To provide a stainproofing agent which can provide a resin excellent in resistance to greasy stains, and its durability against rubbing, abrasion, and steam.

Antioxidant molecules 3 having rubbing and abrasion resistance and oil repellency are dispersed in a general purpose resin 2. Near the surface of the resin the moieties of antioxidant molecules are present inside the resin because of their good compatibility with the resin, whereas the oil-repellent moieties of the molecules are oriented to establish a state in which they are exposed to the surface air layer because of their incompatibility with the resin. The oil-repellent antioxidant molecules 4 are oriented on the surface of the resin until a closely packed state is reached, whereas the extra oil-repellent antioxidant molecules are present in a state in which they are dissolved in the resin. Even if the oil-repellent antioxidant molecules 4 are partly removed from the surface of the resin by rubbing or abrasion, the oil-repellent antioxidant molecules 4 dissolved in the resin are diffused into the surface of the resin to replenish the defects to thereby keep the surface oil-repellent.