Cartridge in which disk is stored

A cartridge (6) comprises upper and lower half segments (2), (3) butting against each other and containing a disk (60), a shutter (4) provided on one side of the cartridge half segments (2), (3) for exposing or alternatively enclosing the disk (60), and a torsion spring (5) attached to the shutter (4) for biasing the shutter (4) in a closing direction. An insertion opening (31) is formed in a side portion of the cartridge (6) for permitting insertion of the torsion spring (5) therethrough from outside, and a protective wall (20) is provided upright between the insertion opening (31) and the disk (60) to define a space by the wall and the upper half segment (3). The space is so sized as to permit the torsion spring (5) to pass therethrough while leaving a small clearance, with legs (51) thereof directed laterally.