A hard disk drive is disclosed which is highly reliable against environmental changes. A
breather hole is formed in an
enclosure which houses therein a magnetic disk and a magnetic head. An opening / closing control mechanism is provided in the
breather hole. The opening / closing control mechanism is made up of a valve member for opening and closing the
breather hole, a lever which supports the valve member at a fulcrum, a spring which urges the valve member in a closing direction through the lever, and a solenoid which causes the valve member to be displaced in an opening direction against the biasing force of the spring. When the hard disk drive is not operating, the breather hole formed in the
enclosure 1 is closed to seal the
enclosure hermetically. The breather hole is opened only in an operating condition of the hard disk drive in which the
internal temperature of the enclosure rises, thereby minimizing an environmental deterioration in the interior of the enclosure caused by
moisture, gases and particles entering from the exterior and preventing a lowering of reliability caused by
corrosion of the magnetic disk and the magnetic head.