The present invention relates to a disk cartridge in which a disk-like recording medium such as an optical disk, a magneto-optical disk and a magnetic disk is accommodated within a disk compartment of a cartridge housing, a disk recording medium device in which the disk-like recording medium is accommodated in advance within the disk compartment so as to become freely rotatable and a disk recording and/or reproducing apparatus for recording and/or reproducing information by using this disk recording medium device.A disk cartridge according to the present invention comprises a cartridge housing in which a disk compartment is formed by combining an upper shell and a lower shell and in which an opening portion is formed on the lower shell and the like and a pair of shutter members provided on the cartridge housing so as to become movable between the opening position at which the opening portion is opened and the closing position at which the opening portion is closed and which has joint portions that are joined to each other at the closing position, wherein a rectangular groove portion and a rib portion that can be engaged with each other are provided on each joint portion of a pair of shutter members over approximately the total length of the joint portion.According to the present invention, a dust-proof property of the joint portions, which are joined to each other, of a pair of shutter members can be enhanced. Thus, it is possible to provide the disk cartridge, the disk recording medium device and the disk recording and/or reproducing apparatus in which dusts, smudges and so on are difficult to enter the disk compartment.