PURPOSE: To reduce a reoccurrence probability of a reading error with sespect to the rewriting method of the magnetic disk device performing reading/writing in accordance with a reading error occurrence.

CONSTITUTION: A patial responce equalization is carried out for a signal read out by a head 2 from a magnetic disk 1 by an equalizing circuit 3, the equalized output signal of the equalizing circuit 3 is identified, data is reproduced and a retrial is carried out by the generation of the reading error. The characteristic of the nikist equalizing circuit constituted of the low pass filter 4 and the equlizing part of the equalizing circuit 3 is changed, a waveform interference quantity on the adjacent identifying point of the equalized output signal is changed, the probability of improvement of S/N on the identifying point is enhanced and the operations of the reading/writing are carried out.