A servo writer includes a tape running drive unit for running a magnetic tape in a longitudinal direction; a pulse signal generating circuit for generating pulse signals; a write head having a plurality of linear magnetic gaps thereon in a running direction of the magnetic tape at a predetermined interval, inputting pulse signals generated by the pulse signal generating circuit, and writing servo patterns corresponding to the magnetic gaps onto the magnetic tape with pitches between the servo patterns; a read head for sensing the servo patterns written on the magnetic tape and outputting pulse signals corresponding to the sensed servo patterns; a control unit for controlling the tape running drive unit to maintain constant the running speed of the magnetic tape based on a time interval between the pulse signals resulted from two of the appropriate linear patterns in parallel included in each of the servo patterns.