The present invention relates to a method and an apparatus for determining eccentricity of a magnetic disk. According to the method and apparatus of the invention, it is possible to monitor the eccentricity of a pre-formatted servo pattern on a disk so as to mount a tool for forming the servo pattern suitably or to rest above a plurality of magnetic disks tidily during an operation period. The method of the invention includes the following steps: measuring jumpiness of an external diameter of the magnetic disk by using a displacement monitor arranged in a first fixed angular position; decoding servo pattern information of the magnetic disk by using a recording head arranged in a second fixed angular position; and associating the jumpiness and the servo pattern information to determine departure information that the center of the servo pattern departures from the center of the magnetic disk defined by the external diameter.