A magnetic head device which suppresses output fluctuation even though the output changes in part of an output waveform from the magnetic head. The magnetic head device includes a magnetic head for reproducing information recorded in a magnetic information recording medium; an amplifier section for amplifying a reproduced signal that the magnetic head has reproduced, by using a gain; an A/D converter section for converting the reproduced signal that has been amplified, to a digital signal, by sampling the signal at predetermined intervals, in order to output the converted digital signal; a signal comparator section for comparing a digital signal output value with a predetermined output criterion value; and a gain control section for adjusting the gain in such a way as to make the output value closer to the output criterion value, in the case where the output value is either greater or smaller than the output criterion value.