An oil-circulating structure for fan has an oily bearing with a central axis hole for pivoting a fan shaft. An oil-collecting recess trench is formed on the inside wall of the axis hole. The oil-collecting recess trench has a double inner screw shape oil-guiding ditch that is separately formed in clockwise and anti-clockwise direction and forms a plurality of crisscrosses in the oil-collecting recess trench. When the fan rotates, a lubricant in the oil-collecting recess trench is driven by the rotating fan shaft to flow the crisscrosses through the double inner screw shape oil-guiding ditch to circulate in the oil-collecting recess trench so as to achieve an internal-recycle oil-circulating system.