To obtain the subject additive comprising an inorganic powdery material mixed with a liquid fluorine atom-containing organic compound and capable of imparting excellent water repellency and excellent oil repellency to powder coatings.

This additive comprises a powdery mixture obtained by mixing (A) 100 pts.wt. of an inorganic fine powdery material having a specific surface area of ≥2m2/g (preferably silica, alumina, titania) with (B) 1-200 pts.wt. of a fluorine atom-containing organic compound which is liquid at 5-50°C. The component A is preferably preliminarily subjected to a hydrophobic surface- forming treatment using a silane treating agent. The additive is preferably added to the powder coating composition in an amount of 0.1-50wt.%, preferably 0.5-30wt.%. The addition of the additive to the powder coating enables to form coating films excellent in water repellency and oil repellency to various kinds of substrate surfaces.