A magnetic disc drive apparatus in which a magnetic disc rotating section and a head arm having a magnetic head are accommodated within a casing and a main printed circuit board is attached to a bottom surface side of the casing is comprised of an auxiliary printed circuit board having at least a recording/playback amplifier, a playback side frequency characteristic circuit and a playback side pulse shaping circuit and which is accommodated within the casing, the auxiliary printed circuit board being connected to the magnetic head and the main printed circuit board. Thus, recording/reproducing signals can be prevented from being deteriorated by inside or extraneous noise and space for assembly parts on the main printed circuit board can be saved.