Embodiments of the present invention help to prevent leakage of low-density gas during low-density gas injection into a disk drive device and to perform low-density gas injection efficiently. In a hard disk drive (HDD) according to one embodiment of the present invention, an injection hole filter with a valve function is attached to a helium injection hole in order to inject helium gas in an enclosure. The injection hole filter has a valve member configured to operate in an open state or closed state. The open state is a state while the helium gas is being injected and the closed state is a state after the helium gas has been finished to be injected. The valve member is in the open state if the outside pressure is higher than the inside pressure and is in the closed state if the inside pressure is higher than the outside pressure.