In a positioning control apparatus, a distance between an actual position at
which
absolute values of N and Q head positioning signals whose amplitudes vary cyclically
in accordance with a position of a magnetic head and whose phases are different
from each other by 90 degrees are equal to each other and an optimum position at
which the absolute values of N and Q head positioning signals should be equal to
each other is calculated from a deviation of an actual position of the magnetic
head with respect to a target value of zero which deviation is obtained when controlling
the magnetic head to be positioned at a boundary between ranges in which the N
and Q head positioning signals have respective linearities so that the absolute
values of N and Q head positioning signals become equal to each other.
