A cartridge retaining mechanism equipped in a nucleic acid extracting
apparatus for extracting a nucleic acid, the mechanism comprising: a
cartridge that comprises: a cartridge main body that has a cylindrical
shape with a bottom, and the bottom is shaped in a funnel shape; a
nucleic acid-adsorbing solid carrier that traps a nucleic acid, and the
carrier is disposed at the bottom; and a cartridge cap that is detachably
mounted on an open end of the cartridge main body, a supporting part that
supports the cartridge; and a pressure-proof retaining part that pushes
the cartridge cap, wherein a cylindrical rib with a diameter smaller than
a diameter of the cartridge main body is formed on an upper plane of the
cartridge cap so that the cylindrical rib protrudes from the upper plane;
a nozzle-receiving opening to which a pressure nozzle is pressed is
formed at the cylindrical rib; and an aperture through which the
cylindrical rib is inserted is formed in the pressure-proof retaining
part, and wherein when the pressure nozzle is pressed to the
nozzle-receiving opening, along with the nozzle-receiving opening being
exposed from the aperture, the cartridge cap is pressed by the
pressure-proof retaining part and simultaneously the cartridge main body
is supported by the supporting part.