In an in-vehicle navigation apparatus, a present position is detected, an altitude of the present position is acquired from map data, and a temperature inside of a hard disk drive is acquired with a temperature sensor. An atmospheric pressure of the present position is then calculated from the altitude and temperature. When the calculated atmospheric pressure is less than a predetermined atmospheric pressure, it is presumed that a magnetic head cannot be floating against a magnetic disk in the hard disk drive. Access to the hard disk drive is thereby prohibited. Thus, in the hard disk drive of the navigation apparatus, contact between the magnetic head and the magnetic disk is prevented when running a place with a low atmospheric pressure.