A servo writer which writes a servo mend on a tape by the write head is characterized
by being equipped with a pay-off side motor paying off the tape from tie payoff
reel by rotating the pay-off reel; a winding side motor winding the tape on the
winding reel by rotating the winding reel; a first capstan roller and second capstan
roller which are provided at an upstream side and down stream side of the write
head, respectively, and by rotating the capstan rollers, run the tape in a state
pinched between respective pinch rollers and the capstan rollers; a first tension
detector which is provided between the first capstan roller and second capstan
roller and detects running tape tension; and a capstan roller controlling unit
controlling a rotation speed of the first capstan roller and second capstan roller
so that tension detected by the tension detector becomes constant.
