Disclosed is a recording disk cartridge which improves its assembly and production capacities, as well as the flexibility of the design. The recording disk cartridge that has a cartridge case including flexible recording disk media in an integrally rotatable fashion, a lower plate forming a lower wall of the cartridge case, the lower wall being placed parallel to the recording disk media, one or more inner plates being fixed on the lower plate with being stacked and partitioning the recording disk media, and an upper plate being fixed on the inner plates and forming an upper wall of the cartridge case. Furthermore, the lower plate incorporates at least one of a shutter lock mechanism and a write protect switch mechanism. The shutter lock mechanism blocks a shutter from being opened, and the write protect switch mechanism prevents data from being erased accidentally from the recording disk media.