The present invention relates to an oleophilic antimicrobial composition comprising silica nanotubes containing silver nanoparticles. The composition is added to an oil-based composition, such as an oil-based paint, a ceramic composition or a fiber coating compositions, immediately before the use of the oil-based composition, such that the contact time of the silver nanoparticles with the organic solvent contained in the oil-based composition is shortened to inhibit the oxidation of the silver nanoparticles. In addition, the composition has improved antimicrobial effects due to the excellent dispersibility of the silver nanoparticles, because the silver nanoparticles do not agglomerate in any solvent due to the silica nanotube structures, unlike spherical silica structures.