To provide a magnetic disk device capable of efficiently recovering the error when the read error is generated, by retrying the read while effectively suppressing the fluctuation of a base line.

By the magnetic disk device, data recorded on the magnetic disk are read out for reproduction through a magnetic head. This magnetic disk device is provided with plural band-pass filters 4, each of which has the specified band width, a read data processing circuit 5 for fetching a signal which is passed through the band-pass filter 4 while being read in through the magnetic head, and outputting it as the read data, and a width selecting circuit 6 for selecting the band width of the band-pass filter 4 when the output of the read data processing circuit 5 does not satisfy the prescribed condition.