A multi-stage gasket having a multi-stage structure constituted by multiple kinds of gasket materials and being used by holding between a cover plate and a base plate, the multi-stage gasket having contactness of a gasket as the lowermost layer to the cover plate or the base plate in contact with the gasket that is higher than contactness of a gasket as the uppermost layer to the cover plate or the base plate in contact with the gasket. A gasket can be provided that provides good reworkability of a cover plate and a base plate of a hard disk device, provides sufficient adhesiveness of the gasket to a cover plate and a base plate even when used in a high humidity and temperature environment, and is prevented from being toppled sideways or peeled off even when applied with a force in an oblique direction.