To expand an application field of a magnetic disk device and electronic equipment including the disk device, by applying a device to a casing for accommodation of the disk device to relax installation environmental conditions with respect to humidity which constitutes a restriction in the use of the disk device.

The electronic equipment casing having a pressure control hole 3 in a part of a casing 2 is arranged so that an interior humidity of the casing is made lower than a humidity of external air by increasing the interior temperature of the casing by a set value higher than the external air by a heat generated by an HDD (magnetic disk drive) 1. By this constitution, movement of the inside heat is carried out through natural ventilation from an outside surface of the casing to the external air for heat radiation, and the external air is not drawn directly into the interior of the casing. After the electronic equipment is set in a low sound environment prior to its activation under control of temperature sensors 7 and 13, a temperature of the external air at the installation location is increased, and the HDD or the air in the vicinity thereof is heated by a heater 6 for one hour so that the temperature of the HDD does not become lower than that of the external air, thus preventing condensation.