the embodiment as shown by the drawing the holder arms 10 a and 10 b installed to the disk holder 5 are formed to hold the disk 4 although when the disk holder 5 is attached to the disk cartridge main body 1 a the holder arms 10 a and 10 b are elastically deformed by the arm regulating members 11 a and 11 b and are released from holding the disk 4 when the disk holder 5 is detached therefrom the holder arms 10 a and 10 b recover to original shapes and hold the disk 4 thereby when the disk holder 5 is detached the disk holder 5 can be detached along with the disk 4 in this case an operator does not directly touch the disk 4 and therefore fat oil or the like of the hand does not adhere thereto an explanation will be given of a method of moving the disk 4 held by the disk holder 5 to a disk cartridge having different shape and size in reference to fig3 and 4 fig3 is a view showing a disk cartridge main body 1 b having shape and size different from those of the disk cartridge 301 a in correspondence with the disk holder 5 of fig1 the disk cartridge main body 1 b is a disk cartridge larger than the disk cartridge main body 1 a the disk cartridge main body 1 b is arranged with a shutter 3 b and a shutter spring 2 b similar to the disk cartridge main body 1 a further arm regulating members 11 c and 11 d for elastically deforming the holder arms 10 a and 10 b are arranged at inside thereof different shapes are also constituted for left and right arm regulating.