A recording disk cartridge is provided which includes a plurality of flexible recording disk media stacked inside a cartridge case so as to rotate integrally. The cartridge case includes a lower plate for constructing a lower wall parallel to the plurality of recording disk media, a plurality of inner plates which are stacked and fixed on the lower plate and partition the plurality of recording disk media, and an upper plate which is stacked and fixed on the plurality of inner plates and constructs an upper wall of the cartridge case. An opening is formed in a part of a side wall constructed of the lower plate, the plurality of inner plates, and the upper plate. The recording disk cartridge further includes a lower rotor and an upper rotor supported on inner sides of the lower plate and the upper plate respectively so as to rotate, and a shutter plate having a height corresponding to a height of the stacked recording disk media. The shutter plate is engaged with the upper rotor and the lower rotor so as to open and close the opening.