A storing unit stores first correction information for correcting a distortion synchronized with a rotation frequency of servo information of a first disk. A control unit controls positioning of a head on a target track by correcting the servo information of the first disk with the first correction information. Measurement information used for measuring the first correction information is calculated based on second correction information for the servo information in other disk apparatus including a second disk on which the servo information is formed using a common master medium with the first disk.