We have studied the coercive force of fine magnetic CoPt dot enhanced by nanometer-sizing of the dot. The 39- to 106-nm-sized CoPt magnetic dot arrays were formed by30-keV-electron beam (EB) drawing with thin calixarene resist and 200-eV-Ar ion milling. Using the fine magnetic dot arrays, we measured coercive forces of the dot by x-ray magnetic circular dichroism (XMCD) with an energy of 11.56 keV, which corresponds to an energy edge of Pt-L3. It is experimentally demonstrated that a coercive force of the nanometer-sized magnetic column increased as the dot diameter decreased.