A cartridge for an information recording medium includes a cartridge case, an opening cover, detachably mounted to a rear side opening of the cartridge case, for enabling the information recording medium to be withdrawn or inserted with respect to the cartridge case, and a holding unit for preventing movement of the information recording medium by supporting the information recording medium when the information recording medium is received and/or withdrawn into/from the cartridge case. The holding unit includes a pair of elastic pressure parts, elastically formed on the opening cover, for elastically supporting the information recording medium to prevent movement of the information recording medium when the opening cover is not attached to the cartridge case, and a release unit for releasing the pair of elastic pressure parts when the opening cover is attached to the cartridge case so that the information recording medium is rotatable in the cartridge case.