A hard disk device is to be mounted onto a playing apparatus to play data in the hard disk device, and includes a casing, a spindle, a power supply circuit and a VCM coil accommodated within the casing, a recording medium disk rotatably supported on the spindle, an arm mechanism pivotably supported within the casing, and a head slider that is attached to a distal end of an arm of the arm mechanism and configured to detect the data in the recording medium disk. The spindle is configured to be driven by a spindle motor of the playing apparatus without being contacted by the spindle motor. The VCM coil is to be positioned between VCM magnets of the playing apparatus and is configured to drive the pivoting of the arm mechanism based on a drive current supplied from the power supply circuit.