the case in a corner of each of the half cases 54a and 54b is formed a write protector 60 for prohibiting information recording a circular hole 66 is formed in the half case 54a so that the hub 56 provided in the central portion of the magnetic disc 52 is exposed on the edge portion of the circular hole 66 is disposed a circular rim 67 for preventing dust from entering the magnetic disc cartridge 51 through the circular hole 66 the half case 54a of the magnetic disc cartridge 51 is shown in fig6 in the half case 54a is formed a window 62a in which is inserted a magnetic head not shown for recording information on the magnetic disc 52 and reproducing information therefrom a substantially circular surface 63a is formed on the inner wall of the half case 54a so as to house the magnetic disc 52 a hole 64a for the write protector 60 is also formed in the half case 54a a liner 68a fig8 is attached to a portion of the surface 63a of the half case 54a a metal lifter 70 presses the liner 68a upwardly separated from fig6 in fig7 is shown the half case 54b having a window 62b in which is inserted the magnetic head not shown for recording information on the magnetic disc 52 and reproducing information therefrom a substantially circular surface 63b is formed on the inner wall of the case 54b so as to hold the magnetic disc 52 a hole 64b for the write protector 60 is also formed in the half case 54b a center sheet 72 made of hard resin material is provided on the central portion of the half case 54b.