A writer for head positioning information, or a so-called servo track writer allows the read gap to follow a track which has been established on a recording medium or disk. As long as the read gap keeps following the existing track, the write gap is allowed to move along a path extending in parallel with the existing track. The write gap is utilized to write head positioning or servo information into the recording medium along the path. Even when the recording medium suffers from vibration or the like, the read gap can follow the track. The head positioning information can thus be written into the recording medium so as to establish a head positioning pattern at a higher positional accuracy.