An HDD case is provided that enables direct connection of an interface connector and houses an HDD and that is superior in regard to vibration absorption, sound insulation, radiating heat, and waterproofness, and that consists of (1) a rectangular box-like case body, (2) a cover that have a heat sink, mounted via an adhesive synthetic-resin mat, and sound-absorbing materials; (3) a relay board that includes an internal connector fitted with an interface connector of the HDD, an external connector exposed to the outside so as not to protrude beyond the outside surface of the cover when the cover is closed, and wiring that connects the connectors; and (4) a waterproof seal that is applied all along the mating surface between the cover and the opening at the top of the case body and between the cover and the upper opening surface of the external connector.