PURPOSE:To prevent the deformation such as a warp, etc., of the periphery of an opening part by forming the opening part being faced by an information signal write/read means by punching after molding the cartridge of synthetic resins. CONSTITUTION:A connecting piece 33 provided on each of upper and lower halves 31 and 32 is punched out along guide groves 34 for punching by means of a punching device. As a result of punching the connecting piece 33, the upper and lower halves 31 and 32 are formed with the opening parts 9 and 10 for pickup having respectively such one opening part as big enough for exposing outward an optical disk to be housed at the time of setting up as the cartridge in its signal recording surface over the range of its radial direction inward and out, with which each of individual insertion holes 7, 8 for chucking mechanism is also joined to be continuous.
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